Atherectomy apparatus, systems and methods

ABSTRACT

Described here are devices and methods for performing atherectomies. Generally, the atherectomy devices include a handle, a cutter assembly, and a catheter or catheter assembly therebetween. The cutter assembly includes a cutter housing and a cutter having a first cutting element and a second cutting element, each of which can be rotated relative to the atherectomy device to cut occlusive material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/652,352, filed on Oct. 15, 2012 and titled “ATHERECOTMY APPARATUS,SYSTEMS, AND METHODS”, which claims priority to U.S. ProvisionalApplication Ser. No. 61/546,888, filed on Oct. 13, 2011 and titled“ATHERECTOMY APPARATUS, SYSTEMS, AND METHODS”, the content of each ofwhich is hereby incorporated in its entirety.

FIELD

The devices and methods described herein generally relate to treatmentof occluded body lumens, such as the removal of occlusive material froma blood vessel or other body parts.

BACKGROUND

Peripheral and interventional cardiology is a medical specialty thatdeals with treatment of various forms of cardiovascular disease,including coronary artery disease and peripheral vascular disease.Coronary artery disease and peripheral vascular disease can arise due tothe narrowing of the arteries by atherosclerosis (also calledarteriosclerosis). Coronary artery disease generally affects arteries ofthe heart—arteries that carry blood to cardiac muscles and surroundingtissue. Peripheral vascular disease refers to various diseases of thevascular system outside the heart and brain, which carries blood, forexample, to the legs.

Atherosclerosis commonly affects the medium and large arteries, and mayoccur when fat, cholesterol, and other substances build up on the wallsof arteries and form fleshy or hard/calcified structures calledplaques/lesions. FIG. 1 shows an instance of a first normal arterialsegment (100) having a native arterial wall (102), a second arterialsegment (104) with mild atherosclerosis and initial plaque (106)formation on the native arterial wall (108), and a third arterialsegment (110) with severe atherosclerosis and having advanced plaque(112) formation on the native arterial wall (114). As plaque formswithin the native arterial wall, the artery may narrow and become lessflexible, which may make it more difficult for blood to flowtherethrough. In the peripheral arteries, the plaque is typically notlocalized, but can extend in length along the axis of the artery for asmuch as 10 mm or more (in some instance up to 400 mm or more).

Pieces of plaque can break off and move through the affected artery tosmaller blood vessels, which may in some instances block them and mayresult in tissue damage or tissue death (embolization). In some cases,the atherosclerotic plaque may be associated with a weakening of thewall of the affected artery, which can lead to an aneurysm. Minimallyinvasive surgeries may be performed to remove plaque from arteries in aneffort to alleviate or help prevent the complications ofatherosclerosis.

A number of interventional surgical methodologies may be used to treatatherosclerosis. In balloon angioplasty, for example, a physician mayadvance a collapsed, intravascular balloon catheter into a narrowedartery, and may inflate the balloon to macerate and/or displace plaqueagainst the vessel wall. A successful angioplasty may help reopen theartery and allow for improved blood flow. Often, balloon angioplasty isperformed in conjunction with the placement of a stent or scaffoldstructure within the artery to help minimize re-narrowing of the artery.Balloon angioplasty, however, can stretch the artery and induce scartissue formation, while the placement of a stent can cut arterial tissueand also induce scar tissue formation. Scar tissue formation may lead torestenosis of the artery. In some instances, balloon angioplasty canalso rip the vessel wall.

Atherectomy is another treatment methodology for atherosclerosis, andinvolves the use of an intravascular device to mechanically remove(e.g., debulk) plaque from the wall of the artery. Atherectomy devicesmay allow for the removal of plaque from the wall of an artery, reducingthe risk of stretching, cutting, or dissecting the arterial wall andcausing tissue damage that leads to restenosis. In some instances,atherectomy may be used to treat restenosis by removing scar tissue

Current atherectomy treatments suffer from structural and performancelimitations. For example, currently-available atherectomy devices withrotating burrs (e.g., the Diamondback 360® PAD System, fromCardiovascular Systems, Inc.) generally are not configured to captureparticles that are released as the burr grinds/sands tissue, which mayresult in diminished downstream blood flow resulting from particleresidue. Additionally, these rotating burrs may cause hemolysis, and aregenerally limited as an adjunct therapy to angioplasty.

Other systems, such as the JETSTREAM G3® System, from Pathway MedicalTechnologies, include expandable cutters with foldable/movable cuttingwings and vacuum-driven aspiration supplied via a vacuum pump, which maycause the artery to collapse on to the cutter and perforate the arterialwall. Other atherectomy systems may include a side-window eccentriccutter and distal nosecone which receives material from the cutter.Because the nosecone can only hold a limited volume of plaque, a surgeonmay need to repeatedly withdraw the cutter and flush plaque and othermaterial from the nosecone.

It is be desirable to provide improved atherectomy devices and methods.

BRIEF SUMMARY

Described here are devices and methods for removing occlusive materialfrom one or more vessels. Generally, the devices may comprise a handle,a cutter assembly, and at least one catheter connecting the handle andthe cutter assembly. In some variations, the cutter assembly maycomprise a cutter housing having an opening and a cutter. In somevariations, the cutter may comprise at least one helical flute eachforming a cutting blade. In some of these variations, the one or more ofthe cutting blades may have a positive rake angle. In some of thesevariations, the positive rake angle may be at least 20 degrees. In someof these variations, the rake angle may be at least about 40 degrees. Insome of these variations, the positive rake angle may be between 60degrees and 80 degrees. In some variations, at one or more of thecutting blades may have a negative angle. In some of these variations, acutter assembly may comprise a plurality of cutting flutes, wherein atleast one of the cutting flutes forms a cutting blade having a positiverake angle, and wherein at least one of the cutting flutes forms acutting blade having a negative rake angle. In some variations one ormore of the cutting blades may have a relief angle less than or equal to10 degrees. In some of these variations, one or more of the cuttingblades may have a relief angle of about 0 degrees. In some variations,one or more of the cutting blades has a flute angle less than or equalto about 30 degrees.

In some variations, the cutter may comprise a first cutting element anda second cutting element. In some of these variations, at least aportion of the first cutting element may extend from an opening in thecutter housing. In some of these variations, at least a portion of thecutting element may have an outer diameter greater than or equal to anouter diameter of the cutter housing.

In some variations, the at least one catheter may comprise one or moreregions of cut patterns. In some variations, at least one of the regionsmay comprise a helical cut pattern. In some variations, at least one ofthe regions may comprise a brickwork cut pattern. The devices mayfurther comprise a torque shaft configured to rotate the cutter relativeto the at least one catheter. In some variations, the device may furthercomprise an internal conveyor member.

In some variations, the at least one catheter may be configured to bedeflected. In some of these variations, a device may comprise a handle,a first catheter having a proximal portion and a distal portion, asecond catheter having a proximal portion and a distal portion, thesecond catheter moveable between an undeflected configuration and adeflected configuration in which the distal portion of the secondcatheter comprises a first curve and a second curve, and a cutterassembly attached to the first catheter, wherein the distal portion ofthe second catheter is stiffer than the distal portion of the firstcatheter, and wherein the proximal portion of the first catheter isstiffer than the distal portion of the second catheter, and wherein thefirst catheter is moveable relative to the second catheter to change thesecond catheter between the undeflected and deflected configurations.The devices described here may be used to remove occlusive materialsfrom one or more vessels. In some variations, the device may be advancedintravascularly to a target zone, and the cutter assembly may beactivated to cut occlusive material. In some variations, the occlusivematerial may comprise a chronic total occlusion. In other variations,the occlusive may be removed from the interior of a stent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows anatomic views of segments of an artery, cut in section, toillustrate different degrees of atherosclerosis.

FIG. 2 depicts a diagrammatic anatomic view showing the major arteriesof a right leg and typical variations in diameter of the variousarteries.

FIG. 3A depicts a perspective view of an illustrative variation of anatherectomy system as described here. FIG. 3B shows an enlargedperspective view of a distal portion of the atherectomy system shown inFIG. 3A.

FIGS. 4A-4D depict illustrative methods by which an atherectomy systemmay be deployed intravascularly.

FIG. 5A depicts an exploded perspective view of a variation of theatherectomy systems described here. FIG. 5B depicts an assembledcross-sectional side view of the atherectomy system of FIG. 5A.

FIG. 6A is a side view of a portion of a variation of a catheter bodysuitable for use with the atherectomy systems described here. FIG. 6Bdepicts a plane view of the portion of the catheter body shown in FIG.6A opened up into a sheet configuration. FIG. 6C depicts a side view ofan atherectomy apparatus including the catheter body shown in FIGS. 6Aand 6B.

FIG. 7A is a side view of a portion of a variation of a catheter bodysuitable for use with the atherectomy systems described here. FIG. 7Bdepicts a plane view of the portion of the catheter body shown in FIG.7A opened up into a sheet configuration. FIG. 7C depicts a side view ofan atherectomy apparatus including the catheter body shown in FIGS. 7Aand 7B.

FIGS. 8A and 8B depict a perspective distal view and a side view,respectively, of a variation of a representative cutting element asdescribed here. FIG. 8C is a cross-sectional view of the representativecutting element taken along line 8C-8C in FIG. 8B. FIG. 8D is across-sectional view of the representative cutting element, like thatshown in FIG. 8C, cutting into occlusive materials.

FIG. 9 depicts a distal perspective view of a variation of a cuttercomprising first and second cutting elements.

FIGS. 10A-10I depict an illustrative method of machining a variation ofthe cutting elements described here.

FIG. 11 shows a bottom view of a variation of the cutting elementsdescribed here.

FIGS. 12 and 13 show side views of two variations of cutting elementsdescribed here.

FIGS. 14A, 14B, and 14C depict a perspective view, side view, and bottomview, respectively of a variation of a cutting element as describedhere.

FIG. 15 depicts an illustrative method by which one variation of acutting element as described here may be formed.

FIGS. 16A and 16B depict a variation of the atherectomy apparatusesdescribed here.

FIG. 17 depicts a cross-sectional side view of a variation of thecatheter assemblies described here.

FIG. 18A depicts a perspective view of a variation of the atherectomysystems described here. FIG. 18B is an enlarged perspective view of adistal portion of the atherectomy system shown in FIG. 18A. FIGS. 18Cand 18D depict different manners in which the atherectomy system asshown in FIG. 18A may be manipulated.

FIGS. 19A-19E and 19F(1)-19F5 depict various views by which a variationof the atherectomy devices described here may be manipulated within thevasculature.

FIG. 20A is an exploded perspective view of a variation of theatherectomy systems described here. FIG. 20B depicts an assembledcross-sectional side view of the atherectomy system shown in FIG. 20A.

FIG. 21A is a side view of a portion of a variation of a catheter bodysuitable for use with the atherectomy systems described here. FIG. 21Bdepicts a plane view of the portion of the catheter body shown in FIG.21A opened up into a sheet configuration. FIG. 21C depicts a side viewof an atherectomy apparatus including the catheter body shown in FIGS.21A and 21B.

FIG. 22A is an exploded perspective view of a portion of the atherectomysystem of FIGS. 20A and 20B. FIG. 22B depicts an assembled perspectiveview of the components depicted in FIG. 22A. FIGS. 22C and 22D depict amanner in which the atherectomy system shown in FIGS. 20A and 20B may bemanipulated.

FIGS. 23 and 24 depict side views of representative inner cathetershafts for use with the atherectomy systems described here.

FIGS. 25A-25D depict an illustrative method by which the atherectomysystems described here may be used to treat a chronic total occlusion ina blood vessel.

FIGS. 26A-26F depict a method by which the atherectomy systems describedhere may be used to treat in-stent restenosis.

FIGS. 27A-27L depict an illustrative method of machining a variation ofthe cutting elements described here.

DETAILED DESCRIPTION

One of the clinical challenges of atherectomy arises from the nativeanatomy of certain peripheral regions where atherectomy is indicated(for example, in the leg). Accordingly, it may be useful to describe theanatomy of the leg. FIG. 2 shows the anatomy of major arteries of a leg(200) (the right leg is shown for the purpose of illustration). Alsoshown there is the abdominal aorta (202), the left iliac artery (204),the right iliac artery (206), the internal iliac artery (208), theexternal iliac artery (209), the common femoral artery (210), thesuperficial femoral artery (212), the popliteal artery (214), thetibioperoneal trunk (216), the posterior tibial artery (218), theanterior tibial artery (220), and the peroneal artery (222). Thediameters of the peripheral arteries of the leg generally taper fromlarger to smaller in the direction of arterial blood flow from above theknee to below the knee.

The abdominal aorta (202) is the largest artery in the body, and itsdiameter can range from 19 to 25 mm (about 0.75 to about 1 inch). Theabdominal aorta successively branches or divides numerous times betweenthe proximal and distal regions of the legs. Each successive branch ordivision may reduce the diameter of the arteries in the direction ofarterial blood flow from the heart to the feet, and the tortuousity ofthe path generally increases.

The first branching is at the groin, into the left (204) and right (206)common iliac arteries. In the left leg, the left common iliac artery(204) branches into the internal (208) and external (209) iliacarteries. Near the head of the femur bone (224), the external iliacartery (209) becomes the common femoral artery (210) or “CFA”. The CFAfurther connects to the superficial femoral artery (212) or “SFA”. TheSFA connects to the popliteal artery (214), which runs behind theflexible region of the knee. Above the knee, the SFA generally has adiameter of about 5 to 7 mm, or about 0.2 to 0.25 inch. Traversingdistally below the knee (toward the feet), the popliteal artery (214)may further reduce in diameter to about 4 to 4.5 mm (0.157 inch to 0.177inch), and then further to about 3.5 mm (0.137 inch). Traversing furtherdistally, the popliteal artery (214) eventually branches again into theanterior tibial artery (220) and the tibioperoneal trunk (216),resulting in a further reduction in diameter to about 3.0 mm to 2.5 mm(0.118 inch to 0.098 inch). Traversing further distally, thetibioperoneal trunk further subdivides into the posterior tibial (218)and peroneal (222) arteries, further reducing diameter to about 2.0 mm(0.078 inch). Overall, the diameters of the peripheral arteries of theleg vary typically from about 2 mm (below the knee) to about 7 mm (abovethe knee).

Atherectomy devices are usually introduced into the vasculature thoughan iliac artery by either an ipsilateral (i.e., same side) or acontralateral (i.e., opposite side) approach, and typically advancedunder fluoroscopic radiographic image guidance through the CFA and intothe SFA. Currently, nearly all intravascular atherectomy cases areperformed in the SFA, however, in a majority of these cases, potentiallytreatable atherosclerosis exists on multiple levels of the peripheralarteries, both above and below the knee. Accordingly, the devices andmethods described here may be helpful in reaching these potentialatherectomy sites.

Atherectomy Systems and Apparatuses

A. Overview

FIGS. 3A and 3B show a representative embodiment of the atherectomysystems described here. As shown there, the atherectomy system (300) mayinclude an intravascular atherectomy apparatus (302) and a guide wire(304) over which the atherectomy apparatus (302) may be deployed. Theguide wire (304) is preferably silicon-coated or non-coated (bare), orotherwise free of a PTFE coating. It should be appreciated, however,that in some variations the atherectomy systems described here maycomprise a guide wire that includes a PTFE coating, or that does notinclude a guide wire at all.

The atherectomy apparatus (302) generally includes an elongated catheterbody (306) having a central axis. The catheter body (306) may be sizedand configured to be advanced over the guide wire (304) in a bloodvessel from an external percutaneous access site. The access approachcan be ipsilateral or contralateral, and down to the targeted region.For example, FIGS. 4A and 4B depict views of the anatomy of a patientwith a distal portion of the atherectomy apparatus (302) advanced usingan ipsilateral approach to a target region in the anterior tibial artery(220). As shown there, the atherectomy apparatus (302) may be introducedinto an access site (400) in the right iliac artery (400). Conversely,FIGS. 4C and 4D depict views of the anatomy of a patient with a distalportion of the atherectomy apparatus (302) advanced in a contralateralapproach. As shown there, a distal portion of the atherectomy apparatus(302) may be advanced through an access site (404) in the left iliacartery (204), across the iliac bifurcation, and down to the targetedsite (in these figures, the targeted site is shown as a branch of theprofunda artery (406). In order to follow the intravascular path fromthe access site to the target region, the catheter body (306) shouldpossess physical and mechanical properties to allow the catheter body(306) to follow the guide wire through a bending, often tortuousintravascular path, as will be described in more detail below.

The atherectomy apparatus (302) may also include a handle (308) iscoupled to the proximal (i.e., closest to the caregiver) end of thecatheter body (306). The handle may be sized and configured to besecurely held and manipulated by a caregiver outside an intravascularpath. The handle may be manipulated from outside the intravascular pathnear the percutaneous access site, which may allow a caregiver toadvance the catheter body through the intravascular path, which, in theleg, generally becomes more tortuous as one proceeds toward the distalregions of the legs (below the knee and toward the feet). Image guidance(e.g., CT, radiographic, in situ visualization carried on board theatherectomy apparatus or otherwise provided, or another suitableguidance modality, or combinations thereof) may be used to aid inadvancement or positioning of the atherectomy apparatus (302). Thecatheter body (306) may be advanced to provide access to a targetedregion where fat, cholesterol, and other substances have accumulated onthe walls of arteries to form plaques or lesions, which will also ingeneral be referred to as “occlusive materials.”

The atherectomy apparatus (302) may further comprise a cutter assembly(310) at the distal end (e.g. farthest from the handle) end of thecatheter body. Generally, the cutter assembly may act to cut and capturethe occlusive material, and thereby remove occlusive material from theartery, which may open the artery to blood flow. In some variations, thecutter assembly (310) may include a rotatable cutter (312) at leastpartially housed within a concentric cutter housing (314). The cutter(312) may be rotatable within the housing around the central axis of thecatheter body. In the variation shown in FIGS. 3A and 3B, the cutterhousing (314) may be open at its distal-most end such that thedistal-most end of the cutter may project a distance distally from theopen housing (314). In some of these variations, when the cutterassembly (310) is deployed in the targeted region where the occlusivematerials exist, there may be no structure or component of theatherectomy located in front of (i.e., distal to) the cutter assembly,and thus the first region of the atherectomy apparatus to interact withthe plaque is the cutter assembly.

FIGS. 5A and 5B show an illustrative variation of an atherectomyapparatus (500) suitable for use with the atherectomy systems describedhere. As shown there, atherectomy apparatus (500) may comprise a handle(502), a catheter body (504), and a cutter assembly (506), such asdescribed above with respect to FIGS. 3A and 3B. As shown in FIGS. 5Aand 5B, the cutter assembly (506) may comprise a ferrule (508), a cutterhousing (510), and a cutter including a first cutting element (512) anda second cutting element (514). It should be appreciated that theatherectomy apparatus (500) may comprise any suitable cutter assembly,such as those described in more detail below.

The atherectomy apparatus (500) may include a motor (516), which in theembodiment shown in FIGS. 5A and 5B, may be contained within a housingportion (518) of the handle (502). The motor is desirably batteryoperated, either by use of replaceable batteries, by use of rechargeablebatteries, or combinations thereof. A motor controller may desirablyprovide a consistent supply of power through all operating conditions,including no load through excessive torque and stall conditions. Acontrol switch (520) (e.g., slide switch, pushbutton, and/orpotentiometer) may be provided to include an off/on function, and insome instances, one or more of a variety of other control functions,such as ramp up and/or ramp down, and/or variable speed. In somevariations, the motor may run at about 12,000 RPM at 6 volts nominal.The operating parameters can be changed by adjusting the gear ratio.

As shown in FIGS. 5A and 5B, a torque shaft (522) may connect the motor(502) to the cutter. Specifically, the motor (502) may rotate the torqueshaft (522), which may in turn rotate the cutter within the cutterhousing (510) around the central axis of the catheter body. Rotation ofthe cutter of the cutter assembly (506) may cause the first (512) and/orsecond (514) cutting elements to cut occlusive material and convey theocclusive materials into the cutter housing (510) (a process also knownas “debulking”). Preferably, the cutter assembly (506) captures the cutocclusive materials from the blood without the use of any vacuumaspiration (although it should be appreciated that in some variations,vacuum aspiration may assist conveyance of the cut occlusive material).

Additionally, the atherectomy apparatus (500) may further include aninternal conveyor (524) on the torque shaft (522). As occlusive materialis conveyed into the cutter housing (510) by the cutter, the conveyor(524) may convey the cut occlusive material further back (proximally)along the catheter body for discharge outside the patient's body. Asmentioned above, this conveyance may occur without the use of vacuumaspiration assistance. Mechanical conveyance may complement distalcapture. Because it does not require the assistance of vacuumaspiration, mechanical conveyance may minimize the risk of the arterycollapsing around the cutter and the associated risk of perforation.Additionally, this conveyance may maximize the removal of tissue andblood components that have been damaged by contact with the cutterassembly.

B. The Catheter Body

1. Dimensions

For practical purposes, the outer diameter of any section of thecatheter body, including the cutter assembly it carries, may be dictatedat least partially by the anatomy of the intravascular path and theintended target region. Specifically, it may be desirable to maximizethe cutting effectiveness of the cutter assembly by maximizing thediameter of the cutter, while minimizing the potential of puncture ortrauma to the vessel. Additionally, the outer diameter of the catheterbody/cutter assembly may also be dictated at least partially by thediameter of a guide sheath or introducer selected that may be placed atan access site to allow introduction of the atherectomy apparatus intothe vasculature. It may be desirable to select a guide sheath orintroducer sized to minimize pain, trauma, and blood loss during use,and to facilitate rapid closure of the access incision after removal, tothereby reduce the incidence of interventional complications.

As mentioned previously, diameters of the peripheral arteries of the legvary typically from relatively small in regions below the knee (2.0 mm)to relatively large in regions above the knee (7.0 mm). For percutaneousaccess to the peripheral arteries, clinicians typically use guidesheaths sized from 5F (diagnostic) to 7F (interventional).

Assuming, for example, that a 7 French guide sheath would likely be,from a clinical perspective, the largest selected to access the largervessels above the knee (4 mm to 7 mm), and allowing for a reasonableclearance tolerance between the catheter body/cutter assembly and theguide sheath, in some instances the outer diameter of the catheter bodyfor introduction through such a guide sheath may be selected to beapproximately equal to or less than about 2.4 mm. Assuming that a 5 Fguide sheath would likely be, from a clinical perspective, the largestused to access the smaller vessels below the knee (2.5 mm to 3 mm), andallowing for a reasonable clearance tolerance between the catheterbody/cutter assembly and the guide sheath, in some instances the outerdiameter of the catheter body for introduction through such a guidesheath may be selected to be approximately equal to or less than about1.8 mm. Assuming that an intermediate 6 French guide sheath would likelybe, from a clinical perspective, the largest used to access theintermediate vessels near the knee (3 mm to 4 mm), and allowing for areasonable clearance tolerance between the catheter body/cutter assemblyand the guide sheath, in some instances the outer diameter of thecatheter body for introduction through such a guide sheath may beselected to be approximately equal to or less than about 2.2 mm.

It may desirable that the outer diameter of the cutter assembly bemaximized, to maximize the overall cutting area of the atherectomyassembly. When the cutter assembly of an atherectomy apparatus is thedistal-most component of the apparatus, the cutter assembly may lead theway by cutting through the occlusive materials. With regard to thecatheter body, however, there may functional and clinical benefits thatarise when the outer diameter of the catheter body is not maximized tomatch the outer diameter of the cutter assembly. Reducing the diameterof the catheter body relative to the cutter assembly may minimizefrictional contact between the catheter body and the vessel wall. Thismay lessen the force required to advance the catheter body through thevasculature and occlusive material, and may help prevent the catheterbody from dragging against or sticking to tissue structures in thevessel, or otherwise impeding the progress of the cutter assemblythrough the occlusive materials.

For example, it may be desirable that the outer diameter of the catheterbody proximal of the cutter assembly be sized smaller than the outerdiameter of the cutter assembly. In other instances, it may be desirablethat the outer diameter of the catheter body proximal of the cutterassembly be sized equal to or smaller than the outer diameter of thecutter assembly. For example, in the variation of atherectomy apparatus(500) described above with respect to FIGS. 5A and 5B, the catheter body(504) may have an outer diameter less than an outer diameter of thecutter assembly (506).

The reduced diameter of the catheter body may also permit the injectionof radiographic contrast material around the catheter body in the guidesheath. For example, an atherectomy apparatus for introduction through a7F introducer system may have a 2.4 mm diameter cutter assembly and acatheter body having a 2.2 mm diameter. In other variations, anatherectomy apparatus for introduction through a 5F or 6F introducersystem may have a 1.8 mm diameter cutter assembly and a catheter bodyhaving a 1.6 mm diameter, or a 2.2 mm diameter cutter assembly and acatheter body having a 1.6 mm diameter.

2. Catheter Properties

In addition to the anatomical and clinical considerations that may beused in selecting an outer diameter of a catheter body, the catheterbody may also desirably possess certain physical and mechanicalproperties, such as those described immediately below, which may enhancethe function of the catheter body to support and guide passage of thecutter assembly through the intravascular path and the occlusivematerials.

(i) Column Stiffness (Pushability)

One potentially desirable property for the catheter body includes columnstiffness. Expressed in units of inch/foot-pounds, column stiffness isthe capability of the catheter body to withstand an axial load orcompression while resisting bending. Column stiffness can be measuredand characterized in conventional ways, and may be referred to as“pushability” herein. Generally, a higher column stiffness is desirable,and may allow the catheter body to transmit a higher axial force(compression) applied at the handle to the cutter assembly withoutbuckling. Accordingly, it may be desirable that the catheter bodypossess column stiffness sufficient to push the cutter assembly over theguide wire without buckling. A column stiffness of 0.050 inches/lbf orgreater may be desirable for the catheter bodies described here.

(ii) Tensile Stiffness (Pullability)

Another potentially desirable property for the catheter body comprisestensile stiffness. Expressed in units of inch/foot-pounds, tensilestiffness is the capability of the catheter body of withstanding tensionwhile being stretched or pulled before the cross section starts tosignificantly contract (called “necking”). Tensile stiffness can bemeasured and characterized in conventional ways, and may be referred toas “pullability” herein. Generally, a high tensile stiffness may bedesirable, and may allow the catheter body to be pulled proximally alongan intravascular path (e.g., to withdraw the cutter assembly) withoutnecking. A tensile stiffness of 0.050 inches/lbf or greater may bedesirable for the catheter bodies described here.

(iii) Torsional Stiffness (Torquability)

Another potentially desirable property for the catheter body comprisestorsional stiffness. Expressed in degrees/ounce-inch, torsionalstiffness is the capability of the catheter body to transmit arotational load (torque) without untwisting, over-twisting and/ordeforming. Torsional stiffness may be measured and characterized inconventional ways, and may be referred to as “torquability” herein. Thetorsional stiffness may control the capability of the catheter body totransmit a given amount of rotation applied at its proximal end (i.e.,the handle) to achieve a comparable amount of rotation at its distal end(i.e, the cutter assembly). A higher torsional stiffness may bedesirable, to better allow for rotational transmission along theatherectomy apparatus (i.e., around a guide wire), without twisting ordeforming. A torsional stiffness that achieves a 1:1 relationshipbetween rotation applied at the proximal end and the rotation observedat the distal end may be desirable for the catheter bodies describedhere.

(iv) Bending Stiffness (Trackability)

Another potentially desirable property for the catheter body comprisesbending stiffness. Expressed in units of a bend radius (in inches),bending stiffness is the ability of the catheter shaft to bend inresponse to an applied bending force, without breaking or deforming(i.e., without taking a set). Bending stiffness is an extensive materialproperty that can be measured and characterized in conventional ways,and may be referred to as “trackability” herein. Generally, a lowerbending stiffness may be desirable to allow the catheter body to benavigated over a guide wire around sharp bends in the vasculature. Atargeted bending stiffness of 0.5 inches (bend radius) or greater atmid-length of the catheter body may be desirable for the catheter bodiesdescribed here. If the catheter body includes an active deflectioncomponent at its distal end (as will be described in greater detaillater), a targeted bending stiffness of 1.0″ (bend radius) at thedeflectable distal end may be desirable for the catheter bodiesdescribed here. A prescribed minimum bend radius also makes it possibleto coil the catheter body for packaging without taking a set.

Conventionally, trackability is thought to be inversely related topushability/pullability and torquability. That is, greater pushability,pullability, and/or torquability in a catheter body may reduce thetrackability of the catheter body. However, the catheter bodiesdescribed here may balance the pushability, pullability, torquability,and trackability for a given catheter body. The result may be a catheterbody that is trackable, yet also possesses the requisite columnstrength, tensile strength, and torsional stiffness to be sufficientlypushable, pullable and torquable to allow navigation and advancement ofa cutter assembly.

The overall trackability of a given catheter body (in terms of itsability to reliably navigate over a guide wire) may be influenced mainlyby the physical and mechanical characteristics of the catheter body atits distal end. The pushability, pullability, and torquability may beinfluenced mainly by the physical and mechanical characteristics of thecatheter body proximal to its distal end. That is, the overallconfiguration of different regions of a catheter body may impartcharacteristics to the overall length of the catheter body, which mayallow for optimization of the overall pushability, pullability,torquability, and trackability of the catheter body.

3. Illustrative Catheter Body Variations

Generally, the column stiffness, tensile stiffness, torsional stiffness,and bending stiffness for a catheter body may be at least partiallydetermined by its constituent material or materials, the dimensions ofcatheter body (e.g., the interior diameter, the outer diameter, wallthickness, etc.) and other structural features such as patterning.

FIGS. 6A-6C and 7A-7C depict illustrative variations of the catheterbodies suitable for use with the atherectomy apparatuses described here.In these variations, the catheter bodies may be fabricated from a metaltube (for example, a type 304 stainless steel tube or the like). Thedimensions of the tube may depend at least partially on the intended useof the atherectomy apparatus. For example, in some variations the outerdiameter of the tube may desirably be about 2.2 mm, while in othervariations the outer diameter of the tube may be about 1.6 mm.Additionally or alternatively, the wall thickness of the tube maypreferably be about 0.288 mm. Additionally or alternatively, the overalllength of the tube may preferably be about 1437 mm (about 56.56 inches).

A metal tube with some or all of the dimensions described immediatelyabove may provide a high degree of pushability, pullability, andtorquability, the baseline bending stiffness may limit the trackabilityof the catheter body given the length of the catheter body. Accordingly,in some variations, the bending stiffness of the metal tube may beincrementally modulated along the length of the catheter body bycreating zones of cut patterns along at least a portion of the length ofthe catheter body. The cut patterns may be formed in any suitable manner(e.g., via laser cutting), and the zones may impart a desired profile ofbending stiffness over the length of the catheter body. For example, cutpattern zones may be used to incrementally decrease the bendingstiffness in a stepwise fashion from proximal end to distal end, toprovide a minimum bending stiffness conducive to trackability at thedistal end (where trackability is more desirable). The stepwise fashionin which the bending stiffness is decreased may be configured in amanner to help maintain the overall pushability, pullability, andtorquability.

(i) Helical Cut Patterns

In some variations, one or more zones may comprise a helical cutpattern. For example, FIGS. 6A-6C depict a variation of an atherectomyapparatus (600) comprising a catheter body (602), a cutter assembly(604), and a handle (606). Specifically, FIG. 6C shows a side view ofthe atherectomy apparatus (600), FIG. 6A shows a side view of a sectionof the catheter body (602), and FIG. 6B depicts a plane view of thesection of the catheter body shown in FIG. 6A opened up into a sheet. Asshown there, the catheter body (602) may be formed from a tube and maycomprise zones of cut patterns in the form of helical cuts (608) (whichmay be laser cut) that thread around the longitudinal axis of thecatheter body (602). The helical cuts (608) are separated by uncutregions call “posts” (610). The direction (thread) of a given patterncan be characterized in terms of its direction about the axis—a lefthand thread (when viewed from the proximal end, counterclockwise) or aright hand thread (when viewed from the proximal end, clockwise). Thepattern can be further characterized in terms of the arc (630) of thehelical cuts (608) about the longitudinal axis (in degrees), and the arc(640) of the uncut region/post between cuts (610) about the longitudinalaxis (in degrees). The pattern can be further characterized in terms ofthe axial separation of the cuts (in inches) along the axis, which canalso be called the “pitch” (611).

For example, a cut pattern characterized as “Right Hand Thread, 100°Cut/30° Uncut, 0.012″ Pitch” may be used to describes a helical cutpattern that extends clockwise when viewed from the proximal end of thecatheter body, in which the helical cuts thread 100 degrees about thelongitudinal axis of the, the posts between helical cuts extend 30degrees about the axis, and wherein helical cuts are axially separatedby 0.012 inches.

Because the helical cuts take away material from the tube, the bendingstiffness of the tube may decrease, and may allow the tube/catheter bodyto bend more easily (thereby increasing trackability). This change inbending stiffness may be at least partially determined by the arc of thehelical cuts and posts, as well as the pitch of the helical cuts. Thecut pattern just described can be characterized as a “three-post”pattern, which reflects that a ninety-degree region of uncut metalappears in the span of three post; i.e., n×30°=90°, where n=3, thenumber of posts.

In comparison, a cut pattern characterized as “Right Hand Thread, 135°Cut/45° Uncut, 0.012″ Pitch” may be used to describe a helical cutpattern that extends clockwise when viewed from the proximal end of thecatheter body, in which the helical cuts thread 135 degrees about thelongitudinal axis of the, posts between helical cuts extend 45 degreesabout the axis, and wherein helical cuts are axially separated by 0.012inches. This cut pattern can be characterized as a “two-post” pattern,which reflects that a ninety-degree region of uncut metal appears in thespan of two post; i.e., n×45°=90°, where n=2, the number of posts.

As mentioned above, modifying the arc of the helical cuts, the arc ofthe posts, and/or the pitch of the helical cuts may alter thetrackability of the catheter body. For example, increasing the arc ofthe helical cuts may decrease the bending stiffness and increase thetrackability. Conversely, increasing the arc of the posts may increasethe bending stiffness and decrease the trackability. Increasing thepitch may increase the bending stiffness while decreasing the pitch maydecrease the bending stiffness. In some instances, it may be desirablefor the pitch to be between about 0.006 inches and about 0.016 inches. Apitch below 0.006 inches may be difficult to achieve with conventionallaser techniques as little uncut material remains, and in some instancesa pitch above 0.016 inches may lose trackability.

By choosing a cut pattern, and/or by varying the cut pattern in astepwise manner along the length of the catheter body, the bendingstiffness of the catheter body can be incrementally reduced over itslength to impart trackability, and may be done without diminishing thedesired magnitudes of column stiffness, tensile stiffness, and torsionalstiffness to a magnitude below that conducive to pushability,pullability, and torquability. As mentioned above, for some variations,the pitch may be varied between 0.006 inches and 0.016 inches to alterthe bending stiffness.

The catheter bodies may have any number of zones/regions havingdifferent cut patterns (or in some zones, no cut pattern at all). Forexample, in the variation of atherectomy apparatus (600) shown in FIG.6C, the catheter body (602) may comprise a first region (612) extendingfrom the handle (606), a second region (614) extending distally from thefirst region (612), a third region (616) extending distally from thesecond region (614), a fourth region (618) extending distally from thethird region (616), a fifth region (620) extending distally from thefourth region (618), and a sixth region (622) extending distally fromthe fifth region (620). In some variations each region may have a lowerbending stiffness than the regions proximal to that region. In othervariations, each region except the distal-most region may have a lowerbending stiffness that the regions proximal to that region.Additionally, while shown in FIG. 6C as having six regions, it should beappreciated that the catheter bodies may include any number of regions(e.g., one, two, three, four, or five or more), and some or all of theregions may include a cut pattern such as those described here. Forexample, Table 1 includes one variation of cut patterns that may beutilized with a six-region catheter body (602) as shown in FIG. 6C:

TABLE 1 Cut Pattern (Right Hand Region Axial Length Thread) Pitch 1(Most Proximal) 4.0″ Uncut N/A 2 47.04″ 100° Cut 0.012″  30° Uncut 32.0″ 110° Cut 0.010″  30° Uncut 4 2.0″ 110° Cut 0.008″  30° Uncut 5 1.5″110° Cut 0.006″  30° Uncut 6 (Most Distal) .030″ Uncut N/A

(ii) Brickwork Cut Patterns

In some variations, one or more zones may comprise a brickwork cutpattern. For example, FIGS. 7A-7C depict a variation of an atherectomyapparatus (700) comprising a catheter body (702), a cutter assembly(704), and a handle (706). Specifically, FIG. 7C shows a side view ofthe atherectomy apparatus (700), FIG. 7A shows a side view of a sectionof the catheter body (702), and FIG. 7B depicts a plane view of thesection of the catheter body shown in FIG. 7A opened up into a sheet. Asshown there, the catheter body (702) may be formed from a tube and maycomprise zones of cut patterns in the form of brickwork cuts (708)(which may be laser cut) that thread around the longitudinal axis of thecatheter body (702). The brickwork cuts (708) are generally normal tothe longitudinal axis of the catheter body (704), and may form rows(710) of brickwork cuts (708) along the catheter body (704). In each row(710), the brickwork cuts (708) may be separated by uncut posts (712),and rows (710) are separated axially along the longitudinal axis. Thepattern can be characterized in terms of the arc (730) of the brickworkcuts (708) about the longitudinal axis (in degrees), and the arc (740)of the uncut region/posts (712) about the longitudinal axis (also indegrees). The pattern can be further characterized in terms of the axialseparation of the rows (710) along the axis, which can also be calledthe “pitch” (711). The pattern can also be characterized in terms of theoffset between successive rows (in degrees). For example, in somevariations, the positioning of the brickwork cuts (708) and posts (712)in a first row may be offset from those of an immediately adjacent rowby about 45 degrees about the longitudinal axis (this may be referred toas “alternating brickwork” herein). In some variations, each row (710)may comprise four equally-spaced brickwork cuts (708), with successiverows offset in an alternating brickwork manner.

As discussed immediately above, a cut pattern characterized as “BrickWork Cut Pattern, 90° Cut/30° Uncut, 0.011″ Pitch, Alternating” may beused to describe a brickwork cut pattern in which the brickwork cuts ofa row extend 90 degrees about the axis, the posts of a row betweenbrickwork cuts extend 30 degrees about the axis, successive rows areaxially separated by 0.011 inches and a rotational offset by about 45degrees.

The brickwork cut pattern, like the helical cut pattern, takes awaymaterial from the tube, which may reduce the bending stiffness of thetube and may allow the tube/catheter body to bend more easily (therebyincreasing trackability). This change in bending stiffness may be atleast partially determined by the arc of the brickwork cuts and posts,the pitch between rows, and the offset between rows.

The brickwork cut pattern just described can be characterized as a“three-post” pattern, which reflects that a ninety-degree region ofuncut metal appears in the span of three posts; i.e., n×30°=90°, wheren=3, the number of posts.

In comparison, a cut pattern characterized as “Brick Work Cut Pattern,135° Cut/45° Uncut, 0.011″ Pitch, Alternating” may be used to describe abrickwork cut pattern in which the brickwork cuts of a row extend 135degrees about the axis, the posts of a row between brickwork cuts extend45 degrees about the axis, successive rows are axially separated by0.011 inches and a rotational offset of 45 degrees This brickwork cutpattern can be characterized as a “two-post” pattern, which reflectsthat a ninety-degree region of uncut metal appears in the span of twopost; i.e., n×45°=90°, where n=2, the number of posts.

As mentioned above, modifying the arc of the brickwork cuts, the arc ofthe posts, the pitch of the brickwork cuts, and/or the offset betweenrows may alter the trackability of the catheter body. For example,increasing the arc of the brickwork cuts may decrease the bendingstiffness and increase the trackability. Conversely, increasing the arcof the posts may increase the bending stiffness and decrease thetrackability. Increasing the pitch may increase the bending stiffnesswhile decreasing the pitch may decrease the bending stiffness. In someinstances, it may be desirable for the pitch to be between about 0.006inches and about 0.016 inches. A pitch below 0.006 inches may bedifficult to achieve with conventional laser techniques as little uncutmaterial remains, and in some instances a pitch above 0.016 inches maylose trackability.

In transmitting an axial load (pushing or pulling) a catheter bodyhaving a brickwork pattern, as above described, may not undergotwisting, which may be experienced when the catheter body has ahelically-cut pattern. Brickwork patterns may additionally exhibit anincreased column, tensile, and torsional stiffness at a given bendingstiffness.

By choosing a cut pattern, and/or by varying the cut pattern in astepwise manner along the length of the catheter body, the bendingstiffness of the catheter body can be incrementally reduced over itslength to impart trackability, and may be done without diminishing thedesired magnitudes of column stiffness, tensile stiffness, and torsionalstiffness to a magnitude below that conducive to pushability,pullability, and torquability. As mentioned above, for some variations,the pitch may be varied between 0.006 inches and 0.016 inches to alterthe bending stiffness.

The catheter bodies may have any number of zones/regions havingdifferent cut patterns (or in some zones, no cut pattern at all). Forexample, in the variation of atherectomy apparatus (700) shown in FIG.7C, the catheter body (702) may comprise a first region (713) extendingfrom the handle (706), a second region (714) extending distally from thefirst region (713), a third region (716) extending distally from thesecond region (714), a fourth region (718) extending distally from thethird region (716), a fifth region (720) extending distally from thefourth region (718), and a sixth region (722) extending distally fromthe fifth region (720). In some variations each region may have a lowerbending stiffness than the regions proximal to that region. In othervariations, each region except the distal-most region may have a lowerbending stiffness that the regions proximal to that region.Additionally, while shown in FIG. 7C as having six regions, it should beappreciated that the catheter bodies may include any number of regions(e.g., one, two, three, four, or five or more), and some or all of theregions may include a cut pattern such as those described here. Forexample, Table 2 includes one variation of cut patterns that may beutilized with a six-region catheter body (702) shown in FIG. 7C:

TABLE 2 Square Cut Pattern Region Axial Length (Brickwork) Pitch 1 (MostProximal) 4.0″ Uncut N/A 2 47.04″  90° Cut 0.012″  30° Uncut 3 2.0″ 135°Cut 0.012″  45° Uncut 4 2.0″ 135° Cut 0.012″  45° Uncut 5 1.5″ 135° Cut0.012″  45° Uncut 6 (Most Distal) .030″ Uncut N/A

A catheter body having either a helical cut pattern or a brickwork cutpattern can be lined or jacketed with a polymeric material, and furthermay be treated to produce hydrophilic, hydrophobic, or drug binding(heparin, antimicrobial) properties.

4. Catheter Body Rotation

In some variations, the catheter body can be coupled to a post on thehandle that is sized and configured to rotate in response to rotation ofa control knob. For example, the atherectomy apparatus (500) describedabove with respect to FIGS. 5A and 5B may comprise a rotation knob(526). Rotation of the knob may apply torque to the catheter body toselectively rotate the cutter assembly. An indexing mechanism can beprovided to provide stepwise control, with tactile and/or audiblefeedback, so that the caregiver maintains knowledge of the rotationalposition of the cutter assembly without taking their eye off theradiographic or otherwise provided in-situ image.

It is also possible to apply torque to the catheter body by rotating thehandle itself. Selective rotation of the cutter assembly can thus befinely controlled by a combination of control knob manipulation andhandle twisting.

C. The Cutter Assembly

As mentioned above, the atherectomy device may comprise a cutterassembly. The cutter assembly may comprise a ferrule, a cutter housing,and a cutter comprising at least one cutter element. In variations inwhich the cutter assembly comprises a ferrule, the cutter assembly maybe joined to the distal end of the catheter body by the ferrule.

1. The Cutter Housing

As mentioned previously, the cutter assembly may include a housing inwhich a cutter rotates. It may be desirable to maximize the outerdiameter of the cutter assembly (and with it, the cutter housing) tomaximize the cutting area that may be cut by the cutter assembly. Thesize of the cutter assembly may be limited depending on the intendedintravascular path and the region targeted for treatment, to help reducethe likelihood that the cutter assembly will cut or otherwise damage thevessel wall.

In some of the variations described here, a cutter assembly sized forintroduction through a 7 French guide sheath may have an outer diameterof about 2.4 mm (which, in some variations, may be larger than the outerdiameter of a companion catheter body, as described in more detailabove). A cutter assembly having such an outer diameter may be used, forexample, for access to the larger vessels above the knee (e.g., vesselsbetween about 4 mm and about 7 mm). In other variations described here,a cutter assembly sized for introduction through a 5 or 6 French guidesheath may have an outer diameter of about 1.8 mm to about 2.2 mm(which, in some variations, may be larger than the outer diameter of acompanion catheter body, as described in more detail above). A cutterassembly having such an outer diameter may be used, for example, foraccess to the smaller vessels at or below the knee (e.g., vesselsbetween about 2.5 mm and about 4 mm).

The housing may or may not be dynamic (i.e., able to rotate relative tothe catheter body). In variations where the housing is dynamic, thehousing may be configured to rotate at the same speed or at a differentspeed than the cutter elements. Additionally, the cutter housing may bedynamically driven to rotate in the same direction or in a counterdirection relative to the cutter.

The leading edge of the cutter housing, which defines the periphery ofthe distal opening through which the cutter projects, may desirably berounded and does not present a sharp distal edge. In these variations, arounded distal housing may reduce the possibility that the peripheraledges of the housing catch on the wall of the guide sheath duringintroduction therethrough. Additionally, a rounded distal edge may alsotend to glance off tissue without grabbing or catching on the tissue,which may minimize the resistance felt by the atherectomy apparatusduring advancement. It should be appreciated that in some variations thecutter housing may have a sharp or beveled distal edge. In some of thesevariations, the cutter housing may have an inner bevel. In othervariations, the cutter housing may have an outer bevel.

In some variations, the outside diameter of the cutter may be less thanthe inside diameter of the cutter housing to create a desired cuttinggap between the two. A larger gap may produce a larger cutting volume,but too large of a gap may permit tissue to enter the cutter housingwhile bypassing the cutter. Representative dimensions will be describedin more detail later. In other variations, the outside diameter of aportion of the cutter may be greater than or equal to the diameter ofthe cutter housing. In these variations, the cutter may cut a largerdiameter of tissue, which may reduce the likelihood that the cutterhousing rubs against tissue during advancement while cutting, therebyfacilitating advancement of the device.

2. The Torque Shaft

Within the housing, the cutter may be rotationally driven by a torqueshaft. The torque shaft may be, in turn, driven by the motor in thehandle. The torque shaft may be fabricated from any suitable material,preferably one or more materials that may be consistent with thepushability, pullability, torquability, and trackability of the catheterbody, as described above. For example, the torque shaft may comprise ametal braid and/or one or more metal coils, and one or more portions ofthe torque shaft embedded in a polymer, e.g., PEBAX, polyurethane,polyethylene, fluoropolymers, parylene, polyimide, PEEK, and/or PET. Insome variations, the torque shaft may be made from a rigid material suchas plastic, rendered flexible by incorporation of a spiral relief orgroove.

In some variations (such as the torque shaft (522) depicted above withrespect to FIGS. 5A and 5B), the torque shaft may comprises a flexiblewire coil wound about a central lumen. The central lumen may be sized toaccommodate the passage of a guide wire therethrough. The flexible wirecoil may preferably be wound in the same direction as the intendeddirection of rotation of the torque shaft, which may cause the coil toopen up if torsional resistance to rotation is encountered (as opposedto clamping down, which may cause the torque shaft to lock on to a guidewire positioned in the central lumen).

Generally, the torque shaft may be coupled to a cutter of a cutterassembly at or near the distal end of the torque shaft, and may beattached to the motor (e.g., by gearing) at or near the proximal end ofthe torque shaft. In some variations (such as the atherectomy apparatus(500) depicted in FIGS. 5A and 5B), the cutter assembly may include acentral lumen that may communicate with the central lumen/guide wirelumen of the torque shaft.

3. The Geometry of the Cutting Elements

As mentioned above, in some variations, the cutter of a cutter assemblymay comprise multiple cutting elements. For example, in the variation ofthe atherectomy apparatus (500) described above with respect to FIGS. 5Aand 5B, the cutter assembly (506) may comprise a cutter having first(512) and second (514) cutting elements. As shown there, the firstcutting element (512) may be positioned distally of second cuttingelement (514). The first cutting element (512) may comprise one or morecutting edges (528) which may at least partially project beyond thedistal end of the cutter housing (510). In some variations, at least aportion of the first cutting element (512) may have a diameter greaterthan or equal to the diameter of the cutter housing (510). The secondcutting element (514) may be at least partially housed within the cutterhousing (510), and may comprise one or more cutting edges (530). Asshown in FIG. 5B, the cutting edges (530) of the second cutting element(514) may be entirely enclosed within the cutter housing (510).Generally, the first (512) and second (514) cutting elements may bephysically coupled together (e.g., by adhesives or welding) for rotationin unison.

The torque shaft may couple to a journal (532) in the second cuttingelement. When the first (512) and second (514) cutting elements arephysically coupled together, the torque shaft may rotate both the firstcutting element and second cutting element in unison. A proximal flange(534) on the second cutting element (514) may be seated within arelieved proximal groove (536) in the cutter housing (510). The relievedproximal groove (536) may serve as an axial retainer for the first (512)and second (514) cutting elements within the cutter housing.

(i) The First Cutting Element

FIGS. 8A-8D depict an illustrative variation of a first cutting element(800) suitable for use with the cutter assemblies described here. Insome variations, the first cutting element (800) may be machined from ahard metallic material (e.g., 440C stainless steel) and may have agenerally hemispherical configuration that includes at least one helicalflute (802) (shown there as a right-hand twist, although it should beappreciated that the at least one helical flute (802) may have aleft-hand twist). While shown in FIGS. 8A-8D as having two helicalflutes (802), it should be appreciated that the first cutting element(800) may comprise any suitable number of helical flutes (802) (e.g.,one, two, three, four, or more helical flutes). Each cutting flute mayform a cutting blade (803) having a cutting edge (804).

The first cutting element may be machined to shape the structure of thehelical flutes (802) within the desired hemispherical geometry. Whensupported in an extended, distally projecting relationship relative tothe cutter housing (e.g., by virtue of the connection to a secondcutting element, as described in more detail above), the hemispherical,fluted geometry may be sized and configured to optimize the capabilityof the cutting blade or blades to cut through and capture occlusivematerials, while minimizing the risk of the cutting blade or bladesgrabbing or digging into tissue, wrapping tissue, and otherwise causingthe motor to stall and overload.

The geometry of each flute may be purposely shaped for theabove-mentioned purposes, and the flute geometry may be characterizedwith reference to a combination of angles (or ranges of angles),comprising a rake angle, a relief angle, a flute angle, and a helixangle. Additionally, while shown in FIGS. 8A-8D as having ahemispherical outer profile, it should be appreciated that the frontcutting element may any external profile, such as an egg-shaped outerprofile.

(a) Rake Angle

For each flute, the rake angle (806) (best shown in FIG. 8C) can bedefined as the angle measured between (i) a radius (808) drawn from therotational axis of the cutting blade (810) to the most radially distantedge (804) of the blade (803) and (ii) a tangent (810) drawn from theinner face of that blade (803). The rake angle may describe the angle ofthe cutting edge (804) relative to the material to be cut.

In some variations, each flute of the first cutting element may possessa positive rake angle (i.e., the inner face of the cutting blade slantsinward or back from the cutting edge). The positive rake angle of eachflute is preferably large, and in some instances may be between greaterthan about 20 degrees. In some of these variations, the rake angle ispreferably greater than about 40 degrees. In some of these variations,the rake angle may be between about 60 degrees and 80 degrees (referredherein as a “high” rake angle). In some variations, the rake angle maybe between 65 degrees and 75 degrees. In some variations, the rake anglemay be about 70 degrees.

Generally, a device having a positive high rake angle may be well suitedfor cutting occlusive materials having less calcium, which may have afibrous, fleshy, and/or rubbery consistency. The rubbery consistency maycause conventional cutters to deflect away from these materials, causingconventional devices to lose trackability, but a high rake angle helps acutter slice into this tissue while minimizing deflection of the cutter.Conventional cutter machining techniques generally cannot produce apositive high rake angle cutter, and these cutters generally have asmall rake angle (less than about 15 degrees). Additionally, a largerrake angle may decrease the structural integrity of a cutter, which maythe cutter more likely to chip or break during use. The cuttersdescribed here, however, may allow for the benefits of high rake anglecutting while reducing the risk of cutter malfunction.

The rake angle of the cutter may be modified depending on the nature ofthe tissue to be cut. For example, a cutter assembly intended to cuthard, calcified occlusive materials having a higher calcium content, maybe configured to have a negative rake angle (i.e., the inner face of thecutting blade may slant outward or forward of the cutting edge), whichmay be well suited for grinding or smashing hardened occlusivematerials. It should be appreciated that a given cutting element can bemachined to incorporate cutting blades having both positive and negativerake angles or otherwise include combination of both cutting andgrinding surfaces. For example, in some variations a cutter may comprisea first cutting element having a plurality of helical flutes, wherein atleast one flute has a cutting edge having a positive rake angle and atleast one flute has a cutting edge having a negative rake angle. In someof these variations, the helical flutes having cutting edges having apositive rake angle may have a positive rake angle greater than about 20degrees (e.g., greater than about 40 degrees or about 70°±10°).

In the variation of first cutting element (800) shown in FIGS. 8A-8D,the formation of a flute having a large, positive rake angle (e.g.,70°±10°) may create a cutting blade having an enlarged concave innerface. The enlarged concave inner face may define a trough- orscoop-shaped blade that may efficiently slice through the occlusivematerials (812) as shown in FIG. 8D. The large, positive (high) rakeangle and resulting enlarged concave inner face of the cutting blade mayreduce cutting forces and power requirements for the first cuttingelement (800) and may remove large volume of occlusive materials witheach pass of the cutting blade.

(b) Relief Angle

For each flute, the relief angle (814) can be defined as the anglemeasured between (i) the tangent (816) drawn from the most radiallydistant edge (804) of the cutting blade (803) from radius (808) and (ii)the tangent (818) drawn along the outer face of the blade (803). Therelief angle generally spans the gap between the cutting edge (804) andthe occlusive material (812) surface to be cut (such as shown in FIG.8D). Generally, a smaller relief angle may form a more tangentialinterface with a tissue surface during cutting, which may reduce thelikelihood that a cutting edge may snag or otherwise catch on tissueduring cutting. A larger relief angle may provide more aggressivecutting.

Generally, the relief angle is preferably a small angle less than orequal to about 10° (e.g., between about 0° and about 10°). In some ofthese variations, the relief angle may be about 0°. In some variations,it may be preferable to have a rake angle of about 70 degrees and arelief angle of about 0 degrees. In other variations, a helical flutemay have a rake angle of about 60 degrees and a relief angle of about 10degrees. The formation of a flute with a small relief angle may create acutting edge (804) that may make aggressive contact with the occlusivematerials (812) such as shown in FIG. 8D. Together with a large positive(high) rake angle, a small relief angle may lead to highly efficientcutting and capture of occlusive materials at the distal end of thecutter assembly, minimizing residue and embolization.

(c) Flute Angle

For each flute, the flute angle (824) can be defined in terms of arelationship with the rake angle and the relief angle, as follows:Flute Angle=90°−(Rake Angle)−(Relief Angle)

The magnitude of the flute angle is an indication of how thick and sharpthe cutting edge is. Given that, in a preferred embodiment, the rakeangle may be in a range between about 60° and 80°; the relief angle maybe in a range between of about 0° and 10°, the flute angle may be inrange between about 0° and about 30°. Maximizing the rake angle andminimizing the relief angle to achieve efficient cutting conditions mayresult in a cutter geometry having a reduced flute angle. Accordingly,it may be desirable that the first cutting element be machined from ahard metallic material to include at a cutting edge that is a sharp aspossible. In some variations, is may also be desirable to coat thecutting blade with a biocompatible, highly lubricious material with alow coefficient of friction (preferably no greater than 0.5) to helpkeep the cutting blade sharp during use. In these variations, coatingmaterials such as titanium nitride or diamond-like carbon (DLC) may beused.

(d) Helix Angle

In the variation of the first cutting element (800) shown in FIGS.8A-8D, each flute (802) of the first cutting element (800) may comprisea helical cut. The helix angle (826) may be defined as the angle between(i) the rotational axis (828) of the cutting blade (803) and (ii) atangent (830) drawn along the inner face the cutting blade (803). Themagnitude of the helix angle is indicative of the capability of thecutting blade to transport cut occlusive material proximally along thecutting blade and into the housing.

In some variations, each flute (802) of the first cutting element (800)may have a helix angle (802) between about 30° and 60°. A helix anglebelow 30° may increase the likelihood the first cutting element (800)may overload with occlusive material and stall, while a helix angleabove 60° may diminish the cutting efficiency of the first cuttingelement (800).

(ii) The Second Cutting Element

As mentioned above, the cutter assembly may comprise a second cuttingelement. For example, in the variation of atherectomy apparatus (500)shown in FIGS. 5A and 5B, the cutter assembly (506) may comprise asecond cutting element (514). In variations that include a secondcutting element, the second cutting element may be machined from a hardmetallic material (e.g., 17-4 stainless) to include helical cuttingflutes. The cutting flutes may be configured to have the same rakeangle, relief angle, flute angle, and helix angle as the flutes of thefirst cutting element. In some variations, the above-mentionedgeometries of the first and second cutting elements may be identical,except that the second cutting element has more flutes than the firstcutting element. In some of these variations, the second cutting elementmay have double the number of flutes of the first cutting element; thatis, four flutes are shown.

In some variations, the second cutting element is machined to include ahollow stem that fits within a center journal of the first cuttingelement. For example, in the variation of the atherectomy apparatusshown in FIGS. 5A and 5B, the second cutting element (514) may include astem (538) around which the first cutting element (512) can be placed.For example, FIG. 9 shows a perspective view of cutter assembly (506),in which the first (512) and second (514) cutting elements may be joinedtogether (e.g., by adhesive or welding) in a rotationally alignedcondition. In the aligned condition, two opposing cutting flutes (540)of the second cutting element (514) may be rotationally aligned with thetwo opposing cutting flutes (542) of the first cutting element (512).Their geometries may be matched during machining, and may act to cut andconveyed occlusive material proximally by the first cutting element intothe housing and further convey the occlusive material more proximallyinto contact with the additional cutting blades of the second cuttingelement.

(iii) Two-Stage Cutting Action

The cutter assembly (506) shown in FIG. 9 may provide a two-stagecutting action. Generally, the first cutting element (512) may cutocclusive material and convey the material to the second cutting element(514). The second cutting element (514) may further cut or macerate theocclusive materials into smaller particles. During both cutting actions,the occlusive materials may be continuously captured within the housingand conveyed proximally away from the targeted intravascular site. Whenthe first and second cutter elements rotate, the helical cuttingsurfaces formed by the flutes may cut occlusive materials in the bloodvessel and may convey the occlusive material from the blood vessel intothe housing through the action of the helical flutes, and may do sowithout the assistance of any vacuum aspiration.

4. Machining the Cutting Elements

The cutting elements described above may be machined in any suitablemanner. For example, FIGS. 10A-10I show an example of method by which avariation of a first cutting element as described above may be machined.Specifically, in these variations first cutting element may be formedfrom a metal blank (1000). As shown in FIG. 10A, the metal blank (1000)may comprise a cylindrical portion (1002) and a hemispherical portion(1004) extending therefrom. While shown in FIG. 10A as having ahemispherical portion (1004), it should be appreciated that the distalend of the metal blank (1000) may have any suitable outer profile (e.g.,egg-shaped or the like). A ball mill (not shown) may be used to beginforming a flute (1006), as shown in FIG. 10B (as will be described inmore detail below with respect to FIG. 11). The ball mill may continueto remove material in a circular arc in the hemispherical portion(1004), as shown in FIG. 10C, and then may be drawn proximally along thecylindrical portion (1002) to extend the flute, as shown in FIG. 10D.The ball mill may then exit the blank, as shown in FIG. 10E. The blank(1000) may then be indexed, and a second flute (1008) (as shown in FIG.10F) may be formed in the same manner as described immediately above. Acenter index (1010) may then be formed down the center of the blank(1000), as shown in FIG. 10G, which may allow the first cutter to engagewith a stem of a second cutting element such as described above. Oncethe flutes have been cut from the blank (1000), a proximal portion ofthe blank (1000) may be removed to provide the formed first cuttingelement (1012), as shown in FIG. 10I.

In some variations, the first (1006) and second (1008) flutes may bemilled with a flute helix angle, as shown in FIG. 10H. In thesevariations, the first (1006) and second flute (1008) may be formed inthe same sequence as shown in FIG. 10B-10G, except that the metal blank(1000) is rotated around the longitudinal axis of the metal blank (1000)during formation of the first (1006) and second (1008). The flute helixangle may be any suitable angle, such as described in more detail above.

FIG. 11 shows a bottom view of a variation of a first cutting element(1100) in which a ball mill (1102) may be used to form one or morecutting flutes (1104). The dimensions and relative positioning of thefirst cutting element (1100) and ball mill (1102) may control one ormore characteristics of the cutting flutes (1104). For example, the ballmill (1102) may have a cylindrical portion (1105) having a diameter(1106) and a longitudinal axis (1108), and a hemispherical portion(1110) having a radius (1112). When the ball mill (1102) is initiallyintroduced into cutting element (1100) (such as described above withrespect to FIG. 10B), the ball mill (1102) may be advanced such that thelongitudinal axis of the ball mill (1108) is advanced along a centerline(1114) that intersects with the center of the first cutting element (andin some variations may be perpendicular to the longitudinal axis of theblank). The ball mill (1102) may be advanced along the centerline (1114)until the ball mill forms the desired rake angle, and forms an initialcut such as shown in FIG. 10B. In some variations, the ball mill (1102)may be configured such that the desired rake angle is formed when thecylindrical portion (1105) of ball mill reaches a line (1118) whichperpendicularly intersects the centerline (1114) at the center of thefirst cutting element (1100).

The ball mill (1102) may be moved in an arc relative to the firstcutting element (1100), to extend the cut formed by the ball mill (1102)until the longitudinal axis (1108) of the ball mill (1102) is positioneda distance (1116) away from the centerline (1114), as shown in FIG. 11.When the ball mill (1102) moves in the arc to the position shown in FIG.11, the ball mill (1102) may form a cut as shown in FIG. 10C. In somevariations where the blank comprises a hemispherical end portion, theball mill (1102) may move in an arc having a radius equal to thedistance (1116). Additionally, as the ball mill (1102) moves along thisarc, the longitudinal axis (1108) of the ball mill (1102) may remainparallel with the centerline (1114). As shown in FIG. 11, the ball mill(1102) may form a cutting flue (1104) having rake angle (1120) and arelief angle (1125). For example, in the variation shown in FIG. 11, therake angle (1120) may be about 70 degrees, and the relief angle mayabout 90 degrees.

The ball mill (1102) may be moved distally (e.g., parallel to thelongitudinal axis) to extend the cutting flutes, such as shown in FIG.10D. In some variations, as the ball mill (1102) is moved relative tocutting element (1100) in this way, the distance (1116) between thelongitudinal axis (1108) of the ball mill (1102) and the centerline(1114) may remain constant. It should be appreciated, however, that invariations where the cutting flute (1104) is formed with a helix angle(as described above with respect to FIG. 10H), the first cutter (1100)may be rotated around the center of the cutter as the ball mill (1102)moves between the various positions described above.

The dimensions described above may varied as necessary to provide acutting flute (1104) having a desired rake angle (1124). For example, invariations in which the first cutting element (1100) is configured tohave a diameter of about 2.4 mm and a rake angle (1120) of about 70degrees, the ball mill (1102) diameter (1106) and radius (1112) may beabout 0.0250 inches and about 0.0125 inches, respectively, and distance(1116) may be about 0.0330 inches. In variations in which the firstcutting element (1100) is configured to have a diameter of about 2.2 mmand a rake angle (1120) of about 70 degrees, the ball mill (1102)diameter (1106) and radius (1112) may be about 0.0220 inches and about0.0110 inches, respectively, and distance (1116) may be about 0.295inches. In still other variations in which the first cutting element(1100) is configured to have a diameter of about 1.8 mm and a rake angle(1120) of about 70 degrees, the ball mill (1102) diameter (1106) andradius (1112) may be about 0.0130 inches and about 0.0065 inches,respectively, and distance (1116) may be about 0.0252 inches.

Also shown in FIG. 11, a chamfer bit (1122) may be used to removeadditional material from the first cutting element (1100) between thecutting flutes (1104). For example, FIGS. 27A-27L show such a variationof a method by which a variation of a first cutting element as describedabove may be machined. Specifically, in these variations first cuttingelement may be formed from a metal blank (2700). As shown in FIG. 27A,the metal blank (2700) may comprise a cylindrical portion (2702) and ahemispherical portion (2704) extending therefrom. While shown in FIG.27A as having a hemispherical portion (2704), it should be appreciatedthat the distal end of the metal blank (2700) may have any suitableouter profile (e.g., egg-shaped or the like). A ball mill may introducedalong a centerline (as described in more detail above with respect toFIG. 11) to begin forming a first flute (2706), as shown in FIG. 27B.The ball mill may be moved in an arc to continue to remove material in acircular arc in the hemispherical portion (2704), as shown in FIG. 27C,and then may be drawn proximally along the cylindrical portion (2702) toextend the flute and form cutting edge (2711), as shown in FIG. 27D. Theball mill may then exit the blank, as shown in FIG. 27E. A chamfer bit(or the like) may then be used to form a first cut (2708) (as shown inFIG. 27F) and a second cut (2710) (as shown in FIG. 27G) to removeadditional material from the cutter. The blank (2700) may then beindexed, and a second flute (2712) and second set of cuts (as shown inFIG. 27H) may be formed in the same manner as described immediatelyabove. A chamber bit (or the like) may then be used to reduce the outerdiameter of a proximal portion (2714) of the blank (2700) as shown inFIG. 27I, which may reduce the outer diameter of a proximal portion ofthe cutter (which may provide one or more benefits as described below).A center index (2716) may then be formed down the center of the blank(2700), as shown in FIG. 27J, which may allow the first cutter to engagewith a stem of a second cutting element such as described above. Oncethe flutes have been cut from the blank (2700), a proximal portion ofthe blank (2700) may be removed to provide the formed first cuttingelement (2720), as shown in FIG. 27L.

In some variations, the first (2706) and second (2712) flutes may bemilled with a flute helix angle, as shown in FIG. 27K. In thesevariations, the first (2706) and second flute (2712) may be formed inthe same sequence as shown in FIG. 27B-27J, except that the metal blank(2700) is rotated around the longitudinal axis of the metal blank (2700)during steps used to form of the first (2706) and second (2712). Theflute helix angle may be any suitable angle, such as described in moredetail above.

As mentioned above, in some variations a helical path may be milled intothe cutting flute, but need not. For example, FIG. 12 shows a side viewof a first cutting element (1200) in which the cutting element (1200) isnot rotated around the longitudinal axis (1204) relative to a ball mill(1202) during formation of a first cutting flute (1206). Conversely,FIG. 13 shows a side view of another variation of a second cuttingelement (1300) in which the first cutting element (1300) is rotatedduring formation of cutting flute (1302) to form a helical pathway. Asshown in FIGS. 12 and 13, a proximal segment of the cutting element maybe tapered or otherwise reduced in diameter, which may allow for atleast a portion of the first cutting element to fit within a cutterhousing (not shown) while another portion of the first cutting elementmay have a diameter greater than or equal to the diameter of the firsthousing. This may allow the first cutting element to cut a wider path oftissue relative to the cutter housing, and may reduce the frictionalload on the cutter housing during advancement of the device.

FIGS. 14A-14C depict perspective, side, and bottom views, respectively,of a variation of second cutting element (1400) such as described abovewith respect to FIGS. 5A and 5B. FIG. 15 shows a top view of the secondcutting element (1400) depicted with a ball mill. As shown in thesefigures, the second cutting element (1400) may be machined to have aplurality of helical cutting flutes (1402) (in the variation depictedthere, the second cutting element (1400) may comprise four flutes, butit should be appreciated that the second cutting element may contain anynumber of cutting flutes such as described in more detail above), a stem(1404), a journal (1406) extending at least partially within the secondcutting element (1400), and a guide wire lumen (1408) extending throughthe second cutting element (1400) (including the stem (1404)). In somevariations, some or all of the cutting flutes (1402) may compriseproximal flanges (1410), which may fit at least partially in a groove(not shown) of a cutter housing (not shown) during rotation of thesecond cutting element (1400).

The components may have any suitable dimensions. For example, the secondcutting element may have a first outer diameter (1412) (includingproximal flanges (1410)) and a second outer diameter (1414) (notincluding proximal flanges (1410)). The stem (1404) may have a height(1416) and an outer diameter (1418). The journal (1406) may have adiameter (1420), and the guide wire lumen (1408) may have a diameter(1422). The cutting flutes (1402) may have a height (1419), and theflanges (1410) may have a height (1420). To form the cutting flutes(1402), a ball mill having a tip radius (1424) may be centered adistance (1426) away from a centerline (1428). These dimensions may beat least partially determined by the desired size of the cutterassembly. It should also be appreciated that the cutting element may berotated relative to ball mill (1424) during formation of the cuttingflutes (1402) to provide a helical pathway of the cutting flutes (1402).

For example, in some variations where the second cutting element (1400)is configured to be used with a 2.4 mm cutter assembly, the first outerdiameter (1412) may be about 0.089 inches, the second outer diameter(1414) may be about 0.083 inches, the stem (1404) may have a height(1416) of about 0.064 inches and an outer diameter (1418) of about0.0298 inches, the diameter (1420) of the journal (1406) may be about0.037 inches, the diameter (1422) of the guide wire lumen (1408) may beabout 0.018 inches. In these variations, the cutting flutes (1402) mayhave a height (1419) of about 0.049 inches, and the flanges (1410) mayhave a height of about 0.007 inches. In some of these variations, theball mill may have a tip radius (1424) of about 0.0250 inches and may becentered away from centerline (1428) by a distance (1426) of about0.0330 inches.

In some variations where the second cutting element (1400) is configuredto be used with a 2.2 mm cutter assembly, the first outer diameter(1412) may be about 0.0805 inches, the second outer diameter (1414) maybe about 0.0735 inches, the stem (1404) may have a height (1416) ofabout 0.058 inches and an outer diameter (1418) of about 0.0275 inches,the diameter (1420) of the journal (1406) may be about 0.035 inches, thediameter (1422) of the guide wire lumen (1408) may be about 0.018inches. In these variations, the cutting flutes (1402) may have a height(1419) of about 0.49 inches, and the flanges (1410) may have a height ofabout 0.007 inches. In some of these variations, the ball mill may havea tip radius (1424) of about 0.0220 inches and may be centered away fromcenterline (1428) by a distance (1426) of about 0.0295 inches.

In some variations where the second cutting element (1400) is configuredto be used with a 1.8 mm cutter assembly, the first outer diameter(1412) may be about 0.063 inches, the second outer diameter (1414) maybe about 0.057 inches, the stem (1404) may have a height (1416) of about0.052 inches and an outer diameter (1418) of about 0.0245 inches, thediameter (1420) of the journal (1406) may be about 0.032 inches, thediameter (1422) of the guide wire lumen (1408) may be about 0.018inches. In these variations, the cutting flutes (1402) may have a height(1418) of about 0.49 inches, and the flanges (1410) may have a height ofabout 0.007 inches. In some of these variations, the ball mill may havea tip radius (1424) of about 0.0130 inches and may be centered away fromcenterline (1428) by a distance (1426) of about 0.0252 inches.

D. Mechanical Removal of Occlusive Materials

As mentioned above, in some variations of the atherectomy apparatusesdescribed here, the atherectomy apparatus includes an internal conveyingmember. For example, the variation of atherectomy apparatus (500) shownin FIGS. 5A and 5B may comprise an internal conveyor (524). Invariations that include an internal conveying member, the internalconveying member may comprises a wire helically wound about the torqueshaft in a direction common with the helical cutting surfaces of thecutter assembly. When a cutter assembly cuts and captures occlusivematerial (e.g., when the helical flutes of a first and/or second cuttingelement conveys cut and captured occlusive materials to the conveyingmember), the conveying member may rotate in common with a torque shaftto convey the cut and captures occlusive materials it receives from thecutter assembly further back (proximally) along the catheter body intothe handle. For example, FIG. 17 shows the variation of atherectomyapparatus (500) described above with respect to FIGS. 5A and 5Bconveying and transferring occlusive material (1700) proximally throughthe apparatus.

The occlusive materials carried back by the conveying element into thehandle may be transferred into a discharge passage within the handle. Atransfer propeller communicating with the discharge passage may becoupled to the torque shaft to rotate in common with the torque shaft,and may act to pump the cut, captured, and conveyed occlusive materialsinto the discharge passage. The discharge passage may include anexternal coupler (e.g., a leur connector) to couple the dischargepassage to an external waste container. The cut and captured occlusivematerials may be conveyed into the waste receptacle, and may be done sowithout need for vacuum aspiration. For example, as shown in FIG. 17,atherectomy apparatus (500) may comprise a transfer propeller (544), adischarge passage (546), and an external coupler (548), which may beconnected to an external waste container (1702) as just described.

In some instances, it may be desirable to convey saline or anotherbiocompatible fluid down the catheter body for mixing with occlusivematerial within the cutter assembly. Mixing the fluid with the occlusivematerials may form a slurry, which may reduce the viscosity of thematerials cut, captured, and conveyed from the vessel by the atherectomyapparatus. This may reduce the load imposed on the cutter assembly andfacilitate the transfer of materials into the waste receptacle. As shownin FIG. 17, the atherectomy apparatus (500) may convey a fluid (1704)from the distal end of the device. In some variations, the fluid (1704)may be conveyed through an internal/guide wire lumen within the torqueshaft (522).

II. Deflectable Atherectomy Systems and Apparatuses

A. Overview

In some variations, the atherectomy systems described here may comprisean atherectomy apparatus configured to selectively dynamically deflectat its distal end (e.g., near a cutter assembly). Additionally, theatherectomy apparatus may be configured to selectively sweep a portionof the atherectomy apparatus, as will described in more detail below.For example, FIGS. 18A-18D show one variation of an atherectomyapparatus (1800) comprising a handle (1802), a catheter body (1804), andcutter assembly (1806). These elements may include any of the featurespreviously described. As will be described in greater detail, thecatheter body (1804) may be configured to dynamically deflect at itsdistal end (where the cutter assembly (1806) is carried) relative thecentral axis of the proximal catheter body (1804), as shown in FIG. 18C.This deflection may occur without axial advancement of the atherectomyapparatus. Additionally, the atherectomy apparatus (1800) may beconfigured to rotate the distal end of the apparatus while deflectedabout the central axis of the proximal catheter body (1804) to sweep thecutter assembly (1806) in an arc (1808) around the central axis, asshown in FIG. 18D. The ability of the atherectomy apparatus (1800) tosweep may allow for the cutter assembly to cut occlusive materials in aregion larger than the outside diameter of the cutter assembly, as willbe described in more detail below.

The atherectomy apparatus (1800) may be used in an atherectomy systemincluding a guide wire (1810), and may be introduced into a blood vesselfrom an external percutaneous access site such as described previouslywith respect in FIGS. 4A-4D. The handle (1802) may be sized andconfigured to be securely held and manipulated by a caregiver outside anintravascular path in a manner previously described to advance thecatheter along an intravascular. Image guidance (e.g., CT, radiographic,or guidance mechanisms, or combinations thereof), may be used to aid thecaregiver's manipulation.

FIGS. 20A and 20B depict a variation of an atherectomy apparatus (2000)configured for use with the atherectomy systems described here. As shownthere, atherectomy apparatus (2000) may comprise a handle (2002), acatheter assembly (2004), and a cutter assembly (2006). As shown there,the cutter assembly (2006) may comprise a ferrule (2008), a cutterhousing (2010), a first cutting element (2012), and a second cuttingelement (2014). The cutting assemblies may have any elements orcombination of elements as described in more detail above. For example,the cutter housing (2010), first cutting element (2012), and secondcutting element (2014) may have any of the elements and dimensionspreviously described with respect to FIGS. 3A-17. In some variations,the first and second cutting elements may each comprise one or morehelical cutting flutes having a rake angle between about 60 degrees and80 degrees, a rake angle less than or equal to 10 degrees (in some ofthese variations, about 0 degrees), a flute angle between about 30degrees and about 0 degrees, and a helix angle between about 30 degreesand about 60 degrees.

Also shown in FIGS. 20A and 20B, the atherectomy apparatus (2000) mayfurther comprise a drive motor (2016), which in some variations may becontained within a housing (2018) of the handle (2002). Also shown thereis a torque shaft (2020) which may be coupled by gearing to the motor(2016) at a proximal end of the torque shaft (2020) and coupled to thesecond cutting element (2014) at a distal end of the torque shaft(2020). The torque shaft rotates the first (2012) and second (2014)cutting elements relative to the cutting assembly, such as described inmore detail above. When the cutter rotates, it may cut and conveyocclusive materials into the cutter housing (2010), and may do sowithout the use of any vacuum aspiration.

The atherectomy apparatus (2000) may also further comprise an internalconveyor (2024), which may convey the occlusive materials from thecutter housing (2010) further back (proximally) along the catheter bodyfor discharge outside the patient's body. In these variations, there maybe no need for use of a vacuum pump.

B. The Catheter Body

1. Overview

As mentioned previously, the atherectomy apparatus (2000) may comprise acatheter assembly (2004). The catheter assembly may have any suitabledimensions, such as described in more detail above. For example, in somevariations, the catheter assembly (2004) may have an outer diameter lessthan or equal to the outer diameter of the cutter assembly (2006), Insome of these variations, the catheter assembly (2004) may have an outerdiameter less than the outer diameter of the cutter assembly (2006). Insome of these variations, a cutter assembly may have an outer diameterof 2.4 mm, and the catheter assembly may have an outer diameter of 2.2mm. The catheter assembly may be configured to balance the columnstiffness (pushability), tensile stiffness (pullability), torsionalstiffness (torquability), and bending stiffness (trackability) of thecatheter assembly, such as described in more detail below.

The catheter assembly (2004) may comprise an outer catheter shaft(2026), an inner catheter shaft (2028), and a sweep tube assemblycomprising an inner sweep tube (2030) and an outer sweep tube (2032).

2. The Outer Catheter Shaft

The outer catheter shaft (2026) may be formed in any suitable manner.For example, the outer catheter shaft (2026) may be formed from a metaltube (e.g., a 304 stainless steel tube). The outer catheter shaft (2026)may have any suitable dimensions. For example, in some variations it maybe desirable for the outer catheter shaft (2026) to be formed from atube having an outside diameter of about 2.2 mm, a wall thickness ofabout 0.288 mm, and a length of about 1347 mm (53.03 inches).

As discussed previously, a metal tube with some or all of the dimensionsdescribed immediately above may provide a high degree of pushability,pullability, and torquability, the baseline bending stiffness may limitthe trackability of the catheter body given the length of the catheterbody. Accordingly, in some variations, the bending stiffness of themetal tube may be incrementally modulated along the length of thecatheter body by creating zones of cut patterns along at least a portionof the length of the catheter body. The cut patterns may be formed inany suitable manner (e.g., via laser cutting), and the zones may imparta desired profile of bending stiffness over the length of the catheterbody. For example, cut pattern zones may be used to incrementallydecrease the bending stiffness in a stepwise fashion from proximal endto distal end, to provide a minimum bending stiffness conducive totrackability at the distal end (where trackability is more desirable).The stepwise fashion in which the bending stiffness is decreased may beconfigured in a manner to help maintain the overall pushability,pullability, and torquability.

For example, FIGS. 21A-21C show one variation of an atherectomyapparatus (2100) comprising a catheter assembly (2102) such as describedabove with respect to FIGS. 20A and 20B and having an outer catheterbody (2103), a cutter assembly (2104), and a handle (2106).Specifically, FIG. 21C shows a side view of the atherectomy apparatus(2100), FIG. 21A shows a side view of multiple sections of the outercatheter body (2103), and FIG. 21B depicts a plane view of a section ofthe outer catheter body shown opened up into a sheet. As shown there,the outer catheter body (2103) may be formed from a tube and maycomprise zones of cut patterns in the form of brickwork cuts (2108)(which may be laser cut) that thread around the longitudinal axis of theouter catheter body (2103). As described above with respect to FIGS.7A-7C, the brickwork patterns may comprise rows (2110) of brickwork cuts(2108) separated by uncut posts (2112), in which rows (2110) areseparated by pitch (2114). In some instances, successive rows (2110) ofone or more of the patterns may be offset, and in some instances one ormore of the patterns may comprise an alternating brickwork pattern.These patterns may be characterized in terms of the arc of the brickworkcuts (2108), the arc of the posts (2112), the pitch (2114), and therotational offset between rows (2110).

In the variation shown in FIGS. 21A-21C some of the pattern regions maycomprise a pattern having a 75° Cut/15° Uncut alternating brick work cutwith a patch that may be in a range between 0.011 inches and 0.014inches.

The brickwork cut pattern takes away material from the tube, which mayreduce the bending stiffness of the tube and may allow the tube/catheterbody to bend more easily (thereby increasing trackability). This changein bending stiffness may be at least partially determined by the arc ofthe brickwork cuts and posts, the pitch between rows, and the offsetbetween rows. The “four-post” brickwork (square) pattern described abovewith respect to FIGS. 21A-21C may allow for trackability of the catheterbody while maintaining pushability, pullability, and torquability. Asindicated above, within a given brickwork post pattern, the pitch may bevaried (e.g., between 0.011″ and 0.014″) to affect the bendingstiffness. By increasing the pitch, the bending stiffness may beincreased, and vice versa.

The catheter bodies may have any number of zones/regions havingdifferent cut patterns (or in some zones, no cut pattern at all). Forexample, in the variation of atherectomy apparatus (2100) shown in FIG.21C, the outer catheter body (2103) may comprise a first region (2113)extending from the handle (2106), a second region (2115) extendingdistally from the first region (2113), a third region (2116) extendingdistally from the second region (2115), a fourth region (2118) extendingdistally from the third region (2116), and a fifth region (2120)extending distally from the fourth region (2118). In some variationseach region may have a lower bending stiffness than the regions proximalto that region. In other variations, each region except the distal-mostregion may have a lower bending stiffness that the regions distal tothat region. Additionally, while shown in FIG. 21C as having fiveregions, it should be appreciated that the catheter bodies may includeany number of regions (e.g., one, two, three, four, five, or six ormore), and some or all of the regions may include a cut pattern such asthose described here. For example, Table 3 includes one variation of cutpatterns that may be utilized with a five-region outer catheter body(2102) shown in FIGS. 21A-21C:

TABLE 3 Square Cut Pattern Region Axial Length (Brickwork) Pitch 1 (MostProximal) 1.181″ Uncut N/A 2 17.0″ 75° Cut 0.014″ 15° Uncut 3 22.0″ 75°Cut 0.012″ 15° Uncut 4 12.9″ 75° Cut 0.011″ 15° Uncut 5 (Most Distal)0.10″ Uncut N/A

As mentioned above, the outer catheter shaft can be lined or jacketedwith a polymeric material, and further may be treated to producehydrophilic, hydrophobic, or drug binding (heparin, antimicrobial)properties.

3. The Sweep Tube Assembly

As mentioned above, the catheter assembly (2004) shown above in FIGS.20A and 20B may comprise a sweep assembly comprising an outer sweep tube(2032) and an inner sweep tube (2030). The outer sweep tube (2032) maybe connected to the distal end of the outer catheter shaft (2026) (e.g.,via coupler (2036)) at a proximal end of the outer sweep tube (2032),and may be connected to the cutter assembly (2006) at a distal end ofthe outer sweep tube (2032).

As will be described in greater detail below, within the outer sweeptube (2032), the inner catheter shaft (2028) may be coupled to theproximal end of the inner sweep tube (2030) (e.g., via inner coupler(2038)). Sliding the inner catheter shaft (2028) in a distal directionmay cause the inner sweep tube (2030) to preferentially bend away fromthe center axis, thereby preferentially deflecting the cutter assemblytoward a side wall of the vessel.

FIGS. 22A and 22B show an exploded and an assembled view, respectively,of a distal portion of the sweep tube assembly of the catheter assembly(2004) of FIGS. 20A and 20B. As will be described in greater detail, theouter and inner sweep tubes may be mutually sized, configured, andassembled to permit preferential bending of the deflectable assemblagein only a single direction.

(a) The Outer Sweep Tube

The outer sweep tube (2032) may be formed from a metal tube (e.g., 304stainless steel). As mentioned above the outer sweep tube (2032) mayhave a distal sweep portion (2034) and a proximal post portion (2036).The distal sweep portion (2034) and the proximal post portion (2036) maybe formed from a single tube, or may be formed separately and joined(e.g., by spot welding). The distal sweep portion (2034) and proximalpost portion (2036) may have any suitable lengths. In some variations,the distal sweep portion (2034) may have an axial length of about 0.450inches and the proximal post portion (2036) may have an axial length ofabout 0.400 inches.

In some variations, the proximal post portion (2036) may comprise a cutpattern (such as one or more of the patterns described above) todecrease the bending stiffness of the proximal post portion (2036). Insome of these variations, the proximal post portion (2036) may comprisea 135° cut/45° uncut alternating brickwork pattern with a pitch of about0.12 inches. The highly flexible nature of such a two-post pattern mayprovide a flexible transition between the outer catheter body (2026) andthe distal sweep portion (2034) of the outer sweep tube (2032).

The distal sweep portion (2034), conversely, may be configured to imparta preferential bending property in a predetermined direction. In somevariations, the distal sweep portion (2034) may comprise a pattern ofclosed, interlocking cuts (which may be laser cut). In the variationshown in FIGS. 20A, 20B, and 22A-22D, the closed, interlocking cuts(2038) may extend in rows that extend around a majority of thecircumference (e.g., 350°) of the outer sweep tube, which may leaving aspine (2040) of uncut material (e.g., about 10° of uncut material) thatextends axially along the distal sweep portion (2034).

In some variations, the interlocking cuts (2038) may comprise chamfereddovetail cuts. These cuts may provide a plurality of rows of materialextending from the spine (2040). The rows (which may have an maximumuncut length of 0.25″ each) may be separated by about 0.007 inches ofchamfered, dovetail cuts (at 67.4°). The interlocking cuts (2038) mayhave any number of dovetail cuts (e.g., twelve dovetail cuts along thecircumference in each row). In some variations, the distal sweep portion(2034) may include with a proximal uncut region (adjacent the proximalpost portion (2036), which may be about 0.01 inches in length) and adistal uncut region (adjacent the cutter assembly, which may be betweenabout 0.025 inches to 0.35 inches). Additionally, in some variations atab (2042) of uncut material may extend beyond the distal end inalignment with the spine (2040), which may form an outer tube alignmentkey, as will be described in greater detail later.

The laser-formed pattern of closed, interlocking cuts as just describedmay resist bending in any direction except in the direction of the spine(2040). When a bending force is applied, the interlocking cuts open topermit the bending to occur in the direction of the spine. Bending forcein any other direction may be resisted, as the interlocking cuts areclosed to resist bending in these directions.

(b) The Inner Sweep Tube

The inner sweep tube (2030) may be fabricated from a metal tube formed(e.g., nitinol). The inner sweep tube (2030) may extend axially withinthe outer sweep tube (2032) and may have any suitable dimensions. Forexample, in some variations the inner sweep tube (2030) may have anouter diameter of about 0.068 inches and an inner diameter of about0.058 inches, and may have a total axial length of about 0.700inches±0.005 inches.

In some variations, the baseline bending stiffness of the inner sweeptube (2030) may be reduced to impart a preferential bending property ina predetermined direction. In some of these variations, preferentialbending may be created using a pattern of open, dovetail cuts (2048). Inthe variation shown in FIGS. 20A, 20B, and 22A-22D, the closed, open,dovetail cuts (2048) may extend around a majority of the circumference(e.g., 350°) of the inner sweep tube (2030), which may leaving a spine(2050) of uncut material (e.g., about 10° of uncut material) thatextends axially along the inner sweep tube (2030). As shown in FIG. 22A,the spine (2040) of the outer sweep tube (2032) and the spine (2050) ofthe inner sweep tube (2030) may be aligned such that spine (2040) andspine (2050) may be positioned on opposite sides of the catheterassembly.

The dovetail cuts (2048) may have any suitable dimensions. For example,in some variations the dovetail cuts (2048) each extend about 0.55inches along the axis of the inner sweep tube (2030), and may includeany number of dovetail cuts (2048). In some of these variations, theinner sweep tube (2030) may comprise eight dovetail cuts, which mayextend about 0.60″ along the spine (2050). Additionally, in somevariations a tab (2052) of uncut material may extend beyond the distalend in alignment with the spine (2050), which may form an inner tubealignment key, as will be described in greater detail later.

The laser-formed pattern of open cuts as just described permitpreferential bending in the direction of the open cuts, away from thespine, until the open cuts come together and interfere in a distal toproximal succession. When a bending force is applied thereto, the opencuts may permit bending, but, as the bending continues, may resistbending as cuts close and interfere. A preformed bending radius maythereby be built into the inner sweep tube.

The inner sweep tube is inserted into the outer sweep tube, and theinner (2052) and outer alignment tabs (2042) may be brought intoregistration (see FIGS. 22A and 22B). The rotationally aligned inner(2052) and outer (2042) tabs may be fitted into an alignment key (2054)on the ferrule (2008) (as shown in FIG. 22B). This fitting may ensurethat the inner and outer sweep tubes may be properly aligned, and mayalso act to prevent relative rotation between the inner and outer sweeptubes. In some variations, and the inner and outer sweep tubes may befixed to the proximal end of the ferrule (e.g., by welding). Asmentioned above (and as shown in FIG. 22A), when the inner (2052) andouter (2042) tabs are rotationally aligned, the spine of the outer sweeptube (2042) may axially aligned with the open cuts (2048) of the innersweep tube (2030) (i.e., the spine (2050) of the inner sweep tube (2030)may rotationally spaced 180° from the spine (2040) of the outer sweeptube (2032)).

As FIG. 22A also shows, the proximal end of the inner sweep tube (2030)may include includes an open boot region (2054) facing at an angle(e.g., about 90°) from the pattern of open dovetail cuts. The open bootregion (2054) may be sized and configured to receive the distal end ofthe inner catheter shaft. It is the inner catheter shaft that may applya bending force to the deflecting assemblage, as will be described ingreater detail later.

(iii) The Inner Catheter Shaft

The inner catheter shaft (2028) of the atherectomy apparatus (2000)shown in FIGS. 20A and 20B may be sized and configured and fabricated ingenerally the same manner as any of the catheter bodies previouslydescribed (e.g., such as the catheter bodies described above in relationto FIGS. 6A-6C and 7A-7C). For example, the inner catheter shaft (2028)may be formed from a metal tube (e.g., a 304 stainless steel tube), andmay have dimensions suitable to allow the inner catheter shaft (2028) tofit within the outer catheter shaft and to accommodate passage of thetorque shaft and conveyor element therein. Representative embodimentswill be described.

The tube of this material and configuration will provide a baselinecolumn stiffness, tensile stiffness, torsional stiffness, and bendingstiffness. In some variations, the bending stiffness of the metal tubemay be incrementally modulated along the length of the catheter body bycreating zones of cut patterns along at least a portion of the length ofthe catheter body. The cut patterns may be formed in any suitable manner(e.g., via laser cutting), and the zones may impart a desired profile ofbending stiffness over the length of the catheter body. For example, cutpattern zones may be used to incrementally decrease the bendingstiffness in a stepwise fashion from proximal end to distal end, toprovide a minimum bending stiffness conducive to trackability at thedistal end (where trackability is more desirable). The stepwise fashionin which the bending stiffness is decreased may be configured in amanner to help maintain the overall pushability, pullability, andtorquability.

FIG. 23 shows one variation of an inner catheter shaft (2300) which maybe used with the atherectomy apparatus (2000) described above withrespect to FIGS. 20A and 20B. In some of these variations, the innercatheter shaft (2300) may have an outside diameter of 0.0670″±0.0005″,an inside diameter of 0.054″+0.001″, and/or an overall length of about1422 mm±1 mm (i.e., about 56″). As shown in FIG. 23, the inner cathetershaft (2300) may comprise a first region (2302) extending from a handle(not shown), a second region (2304) extending distally from the firstregion (2302), a third region (2306) extending distally from the secondregion (2304), and a fourth region (2308) extending distally from thethird region (2306). The fourth region (2308) may be connected to acoupler (2310) for connecting the inner catheter shaft (2300) to aninner sweep tube (not shown), as discussed in more detail above. In somevariations each region may have a lower bending stiffness than theregions proximal to that region. In other variations, each region exceptthe distal-most region may have a lower bending stiffness than theregions distal to that region. Additionally, while shown in FIG. 23 ashaving four regions, it should be appreciated that the catheter bodiesmay include any number of regions (e.g., one, two, three, four, five, orsix or more), and some or all of the regions may include a cut patternsuch as those described here. For example, Table 4 includes onevariation of helical cut patterns that may be utilized with afour-region inner catheter shaft (2300) shown in FIG. 23:

TABLE 4 Cut Pattern (Right Hand Region Axial Length Thread) Pitch 1(Most Proximal)  4″ Uncut N/A 2 51″ 100° Cut 0.012″  30° Uncut 3  0.5″100° Cut 0.008″  30° Uncut 4 (Most Distal)  .04″ Uncut N/A

The pattern shown in FIG. 23 may impart a high degree of columnstiffness to the inner catheter shaft.

FIG. 24 shows one variation of an inner catheter shaft (2400) which maybe used with the atherectomy apparatus (2000) described above withrespect to FIGS. 20A and 20B. In some of these variations, the innercatheter shaft (2400) may have an outside diameter of 0.0610″±0.0005″,an inside diameter of 0.052″+0.001″, and/or an overall length of about1430 mm±1 mm (i.e., about 56″). As shown in FIG. 23, the inner cathetershaft (2400) may comprise a first region (2402) extending from a handle(not shown), a second region (2404) extending distally from the firstregion (2402), a third region (2406) extending distally from the secondregion (2304), and a fourth region (2408) extending distally from thethird region (2406), a fifth region (2410) extending distally from thefourth region (2408), a sixth region (2412) extending distally from thefifth region (2410), a seventh region (2414) extending distally from thesixth region (2412), and an eighth region (2416) extending distally fromthe seventh region (2414). The eighth region (2416) may be connected toa coupler (2418) for connecting the inner catheter shaft (2400) to aninner sweep tube (not shown), as discussed in more detail above. In somevariations each region may have a lower bending stiffness than theregions proximal to that region. In other variations, each region exceptthe distal-most region may have a lower bending stiffness than theregions distal to that region. Additionally, while shown in FIG. 24 ashaving eight regions, it should be appreciated that the catheter bodiesmay include any number of regions as described in more detail above, andsome or all of the regions may include a cut pattern such as thosedescribed here. For example, Table 5 includes one variation of helicalcut patterns that may be utilized with an eight-region inner cathetershaft (2400) as shown in FIG. 24:

TABLE 5 Cut Pattern (Right Hand Region Axial Length Thread) Pitch 1(Most Proximal)  3.789″ Uncut N/A 2  2″ 100° Cut 0.016″  30° Uncut 3 11″100° Cut 0.015″  30° Uncut 4 11″ 100° Cut 0.014″  30° Uncut 5 11″ 100°Cut 0.013″  30° Uncut 6 17″ 100° Cut 0.012″  30° Uncut 7  .5″ 100° Cut0.008″  30° Uncut 8 (Most Distal)  .010″ Uncut N/A

The patterns shown in FIG. 24 may impart more flexibility than thepatterns shown in FIG. 23.

In some instances, there may be a gap between the inner and outercatheter such shafts, such that flushing fluid that may be conveyed downto the cutter assembly, for mixing with occlusive material within thecutter assembly. Mixing the fluid with the occlusive materials may forma slurry, which may reduce the viscosity of the materials cut, captured,and conveyed from the vessel by the atherectomy apparatus to reduce theload imposed on the cutter assembly and facilitate the transfer ofmaterials into the waste receptacle, as has been previously described.An increased gap may provide a greater volume of fluid to the cutterassembly, which may in turn improve the mechanical conveyance ofocclusive materials away from the long total occlusion, thereby reducingthe chance of cutter overload and stalling.

(iv) The Mechanism of Deflection and Sweep

The distal end of the inner catheter shaft may be coupled to the innersweep tube, and may control deflection of the catheter assembly. Forexample, in the variation of atherectomy apparatus (2000) describedabove with respect to FIGS. 20A, 20B, 22A and 22B, the inner coupler(2038) may connect the inner catheter shaft (2028) to the inner sweeptube (2030) via the boot region (2054). Generally, the inner coupler(2038) may join the inner catheter shaft (2028) to the boot region(2054) in a manner that may transmit axial compression or tensile forcesto the inner sweep tube (2030), but accommodates relative rotationbetween the inner catheter shaft (2028) and the inner sweep tube (2028)(i.e., the inner catheter shaft does not rotate when the outer cathetershaft is rotated to rotate the inner and outer sweep tubes).

In the situation where the diameter of the inner catheter shaft isreduced to increase the gap dimension between the inner catheter shaftand the outer catheter shaft (as previously described, to accommodate agreater fluid volume), the coupling sleeve may be sized to locallystep-up the distal diameter of the reduced diameter inner catheter shaftwhere it is coupled to the open boot of the inner sweep sleeve (i.e.,the inner sweep tube need not be downsized when the inner catheter shaftis downsized), but it should be appreciated that in some instances thediameters of these components may be the same.

The proximal end of the inner catheter shaft may be coupled to a controlknob (2056) on the handle (2002). The control knob (2056) may beadvanced axially (distally) to advance the inner catheter shaft (2028)against the inner sweep tube (2030), to thereby apply a compressiveforce (as illustrated by arrow (2058) in FIG. 22D) along the innercatheter shaft (2028) to the inner sweep tube (2030). Being constrainedfrom axial advancement by the ferrule (2008), the inner sweep tube maypreferentially deflect in response to the applied compressive force inthe direction of the open cut regions (as illustrated by arrow (2060) inFIG. 22D). Likewise, the control knob may be retracted axially(proximally) to relieve the compression force and apply a tensile forceto the inner sweep tube, to straighten the delectable assembly, as shownin FIG. 22C.

As shown in FIGS. 22C and 22D, with the spine of the inner sweep tubealigned opposite the spine of the outer sweep tube, the preferentialbending property of the inner sweep tube (in the direction of the opencuts) may be unified with the preferential bending property of theconcentric outer sweep tube (in the direction of the spine, away fromthe close cuts). The inner sweep tube may progressively bend in responseto the bending force imparted by axial advancement of the inner cathetershaft, which may cause the open cuts of the inner sweep tube close andinterfere first at the distal end, followed in succession by closing andinterference of the proximal cuts down the length of the inner sweeptube. This may form a progressive distal-to-proximal stacking pattern asthe inner sweep tube progressively bends until all cuts on the innersweep tube close and interfere to define the full bend radius (which insome variations may be about 1°). The outer sweep tube may bend inconcert with the inner sweep tube, which may open the closed cuts in adistal-to-proximal stacking pattern. The inner and outer sweep tubes maychannel the applied bending force in the direction of preferentialbending, and may require less bending force for a given angular unit ofdeflection. Further, the successive distal-to-proximal stacking of theinner sweep tube cuts and opening of the outer sweep tube cuts mayresult in a uniform column stiffness applied to the cutter assemblyregardless of the degree of deflection.

When deflected, the catheter assembly may apply an apposition force uponthe cutter assembly, which may be created by opposing contact of theouter catheter assembly against an opposite vessel wall when the cutterassembly (deflected at the end of the catheter) contacts the occlusivematerials at a desirable attack angle (as shown FIGS. 19B and 19C). Theunified cooperation of the inner and outer sweep tubes duringpreferential bending may increase the magnitude of the apposition force,and may improve trackability and avoid trauma during advancement overthe guide wire.

In some variations, the outer catheter shaft may be coupled to a post onthe handle that may be sized and configured to rotate in response torotation of the control knob (2056). While axial advancement of thecontrol knob (2056) applies compressive force to the inner cathetershaft to deflect the cutter assembly (as described in more detailabove), rotation of the control knob (2056) may apply a torque to theouter catheter shaft to rotate the cutter assembly. The cutter assemblymay sweep in an arc within the vessel, to clear a diameter of occlusivematerials that is greater than the outer diameter of the cutterassembly. It may also be possible to apply torque to the outer cathetershaft by rotating the handle itself. Selective rotation of the cutterassembly can thus be finely controlled by a combination of control knobmanipulation and handle twisting.

An indexing mechanism may be provided to provide stepwise control ofdeflection and/or sweeping, with tactile and/or audible feedback, sothat a user may maintain knowledge of the rotational position of thecutter assembly without taking their eye off the radiographic image.

(v) Passive and Active Steering

The enhanced, preferential bending properties of the trackable,deflectable catheter assembly may provide the capability to bothactively and passively steer the atherectomy apparatus through tortuousintravascular anatomy. FIGS. 19A-19F(5) depict a manner by which theatherectomy apparatus (2000) described above in relation to FIGS. 20Aand 20B may be actively and passively steered within a vessel.

Active steering may be accomplished by advancement of the inner cathetershaft to bend the distal catheter assembly, accompanied by rotation ofthe catheter assembly, to point the cutter assembly in a preferreddirection through an intravascular path, with or without a guide wire,and/or to point the cutter assembly toward a side wall of a vessel, withapposition, to cut and capture occlusive materials. For example, thecutter assembly (2006) of atherectomy apparatus (2000) may be advancedinto occlusive material (1900) in a vessel (1902), as shown in FIG. 19A.When in place in the vessel, the catheter assembly (2004) may bedeflected as shown in FIG. 19B. The deflected catheter assembly (2004)may be rotated to sweep the cutter assembly (2006), as shown in FIGS.19C and 19D. This sweep may cause the cutter assembly to move in an arcthat is greater than the outer diameter of the cutter assembly. In somevariations, the cutter assembly (2006) may cut in a diameter (D2 asshown in FIG. 19E) at least two times the diameter of the cutterassembly (D1 as shown in FIG. 19E). In other variations, the cutterassembly (2006) may cut in a diameter (D3 as shown in FIG. 19E) at leastthree times the diameter of the cutter assembly. In still othervariations, the cutter assembly (2006) may cut in a diameter (D4 asshown in FIG. 19E) at least four times the diameter of the cutterassembly.

Passive steering may be accomplished without advancement of the innercatheter shaft, when the cutter assembly (2006) encounters a bend in theintravascular path (see FIG. 19F-1). Once the cutter assembly approachesor contacts the bend, the caregiver may rotate the outer catheter body(and thus the deflected catheter assembly) into an orientation in whichthe preferential deflection direction faces away from the inside radiusof the bend (see FIGS. 19F-2 and 19F-3). In the representativeembodiment, this orientation may face the alignment key (2054) on theferrule away from the inner radius of the bend (as can be seen in FIG.19F-3). Due to the preferential bending properties of the catheterassembly when in this orientation, subsequent advancement of the outercatheter shaft, without concurrent advancement of the inner cathetershaft, may apply enough compression force to cause deflection of thecatheter assembly in the preferential direction (i.e., away from theinside radius of the bend). Continuance of the compression force uponthe catheter body may cause the catheter body to follow the passivelydeflected catheter assembly away from inside radius of the bend and intothe bend itself (see FIGS. 19F-3 and 19F-4).

Successive bends in a tortuous path may be navigated in the same passivemanner, by rotating the catheter body at each successive bend (e.g., byrotating the control knob or by rotation of the handle itself) to orientthe preferential deflection of the catheter assembly away from therespective inner bend radius, and without the need to actively steer bymanipulation of the inner catheter shaft.

In some variations, the catheter assembly (2004) may include one or moreradiographic markings to indicate during radiographic guidance theorientation of the preferential bend direction of the catheter assembly,whether left, or right, or toward the viewer, or away from the viewer.

FIGS. 16A and 16B depict another variation of an atherectomy apparatus(1600) described here. As shown there, atherectomy apparatus (1600) maycomprise a first catheter (1602), a second catheter (1604), and a cutterassembly (1605) attached to the first catheter (1602). The firstcatheter (1602) may be moveable relative to the second catheter (1604)to move a distal portion of the atherectomy apparatus (1600) between anundeflected configuration (as shown in FIG. 16A) and a deflectedconfiguration (as shown in FIG. 16B). In the variation of atherectomyapparatus (1600) shown in FIGS. 16A and 16B, the first catheter (1602)may be moveable within the second catheter (1604), although it should beappreciated that in other variations the second catheter (1604) may beslidable within the first catheter (1602).

Generally, a distal portion (1606) of the second catheter (1604) may beshaped to take on a deflected position as shown in FIG. 16B.Specifically, the deflected distal portion (1606) may comprise a doublecurve having a first proximal curve (1608) and a second distal curve(1610). As shown there, the first curve (1608) may bend the distalportion (1606) away from the longitudinal axis (1612) of a proximalportion of the second catheter (1604), while the second curve (1610) maybend the distal portion (1606) in a direction toward the longitudinalaxis (1612). The double-curve configuration of the distal portion (1606)may allow the second curve (1610) to contact or otherwise rest against awall (1614) of a blood vessel (1616), as shown in FIG. 16B.Additionally, this may angle the cutter assembly (1605) toward anopposite vessel wall (1618) during cutting. In instances when theatherectomy apparatus (1600) is advanced over a guide wire (1620) asshown in FIG. 16B, the guide wire (1620) may contact the opposite vesselwall (1618) and may help to prevent the cutter assembly (1605) fromdirectly contacting and/or damaging the vessel wall (1618). In someinstances, the double-curve configuration of the distal portion (1606)may allow for advancement of the distal portion (1606) while deflectedwhile minimizing the risk that the cutter assembly (1605) may catch ontissue and retroflex.

As mentioned above, the first catheter (1602) may be moved relative tothe second catheter (1604) to move the atherectomy apparatus betweendeflected and undeflected configurations. Specifically, the firstcatheter (1602) may comprise a distal portion (1622) and a proximalportion (not shown), where the distal portion (1622) is more flexiblethan the proximal portion. Additionally, the distal portion (1622) ofthe first catheter (1602) may be more flexible than the distal portion(1606) of the second catheter (1604), while the proximal portion of thefirst catheter (1602) may be stiffer than the distal portion (1606) ofthe second catheter (1604). Accordingly, the first catheter (1602) maybe advanced such that the flexible distal portion (1622) of the firstcatheter (1602) extends beyond the distal end of the second catheter(1604), which may the proximal portion of the first catheter (1602)within the distal portion (1606) of the second catheter (1604) (oraround the distal portion (1606) of the second catheter (1604) invariations where the second catheter (1604) is positioned inside thefirst catheter (1602). Because the proximal portion of the firstcatheter (1602) is stiffer than the distal portion of the secondcatheter (1604), axial alignment of these catheter segments may causethe proximal portion of the first catheter (1602) to straighten out thecurves of the distal portion of the second catheter (1604), therebyplacing the atherectomy apparatus (1600) in an undeflectedconfiguration, as shown in FIG. 16A. Because the flexible distal portionof the first catheter (1602) extends beyond the distal portion of thesecond catheter (1604) when in an undeflected configuration, it may beused to track the cutter assembly (1605) along a guide wire duringnavigation of the atherectomy apparatus (1600) through the vasculature.Additionally, the atherectomy apparatus (1600) may be advanced whilecutting to cut along the path of the guide wire (which may be a straightpath in some instances), as described in more detail below. Theatherectomy apparatus (1600) may then be withdrawn and deflected to cuta larger path through occlusive material (not shown), such as describedbelow.

To move the atherectomy apparatus to a deflected configuration, thefirst catheter (1602) may be withdrawn to place the flexible distalportion (1622) of the first catheter (1602) in axial alignment with thedistal portion (1606) of the second catheter (1604). Because the distalportion (1606) of the second catheter (1604) is stiffer than the distalportion (1622) of the first catheter (1602), the second catheter (1604)may cause the flexible distal portion (1622) of the first catheter(1602) to take on the dual-curve configuration described above withrespect to FIG. 16B.

III. Methods of Use

A. Atherectomy in Peripheral Regions

(i) Overview

When atherectomy is indicated, an intravascular atherectomy device asdescribed herein can be introduced into a left or right limb through aniliac artery by an ipsilateral (same side) or a contralateral (oppositeside) approach. In some variations, the atherectomy device may beadvanced over a guide wire, through a guide sheath, and into the bloodvessel. A user may manipulate a handle of the atherectomy apparatus toadvance and navigate the device, and in some instances the advancementmay be aided by radiographic visualization to gain access to thetargeted treatment region, where occlusive materials are located.

The atherectomy device can be advanced distally through the CFA and intothe SFA and, in some variations, further at or below the knee. In somevariations, a catheter body/catheter assembly may have sufficienttrackability to follow the guide wire through the often tortuousintravascular paths to the region targeted for treatment. The catheterbody/catheter assembly may also have pushability, pullability, andtorquability to allow the cutter assembly to be pushed, pulled, and/orrotated through occlusive material in the vessels. The trackability ofthe catheter body while being pushed, pulled, and rotated throughocclusive material may allow the atherectomy apparatus to reliablyfollow the path of the guide wire.

A family of atherectomy apparatus can be provided having thesecombinations of technical features, sized according to the anatomy to betreated and the guide sheaths to be used. For example, an atherectomyapparatus comprising a 1.8 mm cutter assembly supported on the distalend of a 1.6 mm catheter body may be deployed through a 5 F or largerguide sheath for access to smaller vessels (e.g., 2.5 mm to 3.0 mm) forremoval of occlusive materials in one or more straight passes (e.g.,without deflection) through the occlusive materials. Additionally oralternatively, an atherectomy apparatus comprising a 2.2 mm cutterassembly supported on the distal end of a 1.6 mm catheter body, may bedeployed through a 6 F or larger guide sheath for access to largervessels (e.g., 3.0 mm to 4.0 mm) for removal of occlusive materials inone or more straight passes through the occlusive materials.Additionally or alternatively, an atherectomy apparatus comprising a 2.4mm cutter assembly supported on the distal end of a 2.2 mm catheterbody, may be deployed through a 7 F or larger guide sheath for access tolarger vessels (e.g., 3.0 mm to 4.5 mm) for removal of occlusivematerials one or more straight passes through the occlusive materials.

(ii) Increasing Luminal Gain by Deflection and Sweeping

If desired, a given atherectomy apparatus may be sized and configured tobe deflected and swept, so that the cutter assembly be deflected andswept while cutting occlusive materials. For example, a deflectable 2.4mm cutter assembly supported on the distal end of a 2.2 mm catheter bodycan include may be deployed through a 7 F guide sheath to removeocclusive materials in still larger vessels (e.g., 4.0 mm to 7.0 mm). Adeflectable cutter assembly may allow a specific atherectomy apparatusto treat a range of vessel size or vessels that may be asymmetric. Bydeflecting the distal cutter assembly in a controlled fashion in situ,the caregiver may be able to purposefully point the cutter assemblytoward a particular region of the lesion, which may be useful intreating asymmetric vessels.

(iii) Treating Chronic Total Occlusions

Through progressive plaque growth or fibrotic organization of occlusivethrombus, atherosclerosis may result in chronic total occlusion (CTO) ofa major arterial conduit. The success of catheter-based treatmenttechniques may depend significantly upon the nature of the occlusion(e.g., its length, duration, tortuosity, and degree of calcification).Devices sized and configured to cross CTO's preferably possess anability to distinguish a true luminal path from one created within(dissection) or through (perforation) the vessel wall of the occludedsegment; an ability to change direction (steer) to correct deviationsfrom the desired path through the occlusion; and an ability to penetratethe frequently fibrotic and focally calcified substance of the occlusionthrough the use of high cutting efficiency and mechanical stiffness.

The technical features of the highly efficient cutting elementsdisclosed herein, in combination with the degree of trackability coupledwith pushability, pullability, and toquability of the catheter bodiesdisclosed herein, may allow the atherectomy apparatus to be tailored foruse to treat CTO's in the vasculature. For example, FIGS. 25A-25D showone manner in which an atherectomy apparatus (2500) (such as one or moreof the atherectomy apparatuses described previously) may treat a CTO(2502) in a blood vessel (2504) (depicted in FIG. 25A). As shown inFIGS. 25B and 25C, the atherectomy apparatus (2500) may be advanced (forexample, along a guide wire (2506)) while operating a cutter assembly(2508) of the atherectomy apparatus (2500). While cutting, occlusivematerial of the CTO (2502) may be cut and conveyed proximally throughthe atherectomy apparatus (2500). The trackability, pushability,pullability, and torquability of the atherectomy apparatus (2500) mayallow it to follow the path of the guide wire (2506) to recanalize thevessel (2504) (as shown in FIG. 25D).

The atherectomy apparatus described herein may possess the combinationof technical features that may be optimized to cross a CTO and reenterthe distal true lumen from a subintimal location over a guide wire.

(iv) Delivery of Bioactive Materials

It may be desirable, in conjunction with using the atherectomy apparatusas described above, to introduce into the region a bioactive material,comprising, for example, a restenosis-inhibiting agent, athrombus-inhibiting agent, an anti-inflammatory agent, combinationsthereof and the like. The bioactive material can be introduced as acoating on a balloon that may be expanded into contact with the regionto deliver the bioactive material, and/or may be delivered using theatherectomy apparatus.

B. Atherectomy to Treat In-Stent Restenosis

In some variations, the atherectomy systems described herein may be usedto treat in-stent restenosis. As described in more detail above, in someinstances a stent may be placed in a blood vessel (e.g., followingangioplasty). Generally, the stent may act to hold an artery open. Forexample, FIG. 26A depicts a section of an artery (2600) with a stent(2602) positioned therein.

When a stent is placed in a blood vessel, new tissue may grow inside thestent, and may cover one or more portions of the stent. Initially, thisnew tissue may include healthy cells from the lining of the arterialwall, which may allow blood to flow smoothly over the stented areawithout clotting. In some instances, scar tissue or other occlusivematerial may later form underneath the new healthy lining, and mayobstruct the blood flow through the vessel. This condition may bereferred to as “in-stent restenosis”. For example, FIGS. 26B and 26Cshow a cross-sectional perspective view and a cross-section side viewrespectively of the artery (2600) and stent (2602), with occlusivetissue (2604) growing within the stent (2602).

The occlusive tissue (2604) within the stent (2602) is typicallyhyperplastic, smooth muscle tissue, with little calcium, having therubbery, elastic properties of occlusive materials having less calcium,with a consistency that is fibrous and fleshy. For this reason, it maybe desirable for the atherectomy apparatus in these methods to compriseat least one cutting flute having a positive rake angle, such as one ormore of the high rake angle cutting elements described above.Additionally, in some variations it may be desirable for a cuttingelement to have an atraumatic rounded profile (e.g., the hemisphericalprofile of the first cutting elements described in more detail above).Cutting elements having a rounded profile and positive rake anglecutting elements may help prevent a cutting assembly from damaging orotherwise negatively interacting with a stent placed in the vessel.

FIGS. 26D-26F depict one method by which an atherectomy apparatus (2606)(which may be one or more of the atherectomy systems described in moredetail above) may be used to treat in-stent restenosis of the artery(2600) depicted in FIGS. 26B and 26C. As shown there, a guide wire(2608) may be introduced into the artery (2600) and through theocclusive material (2604). The atherectomy apparatus (2606) may beadvanced along the guide wire (2608) and at least partially through theocclusive material (2604), as shown in FIG. 26D. A cutter assembly(2610) of the atherectomy apparatus (2606) may be operated duringadvancement through the occlusive material to cut the occlusive material(2604) and convey cut material proximally, as described in more detailabove (e.g., a conveyor element may convey the tissue from therestenosis proximally along the catheter body for discharge, which mayoccur without supplement of a vacuum pump).

In variations where the atherectomy apparatus (2606) is configured toselectively deflect a distal portion of the atherectomy apparatus(2606), the distal end of the atherectomy apparatus (2606) may bedeflected and rotated to sweep the cutter in an arc. The cutter assembly(2610) may be operated during deflection and rotation to cut tissue in aregion larger than an outer diameter of the cutter assembly (2610, asshown in FIG. 26E. This may be performed along the length of theocclusive material to clear the restenosis within the stent (2602), asshown in FIG. 26F. The result may be the clearing of the restenosiswithin the stent (see FIG. 26F). In some of these variations, theatherectomy apparatus (2606) may be advanced in an undeflectedconfiguration along the path of the guide wire (2608) while cuttingtissue, may be proximally withdrawn, and may be deflected and swept tocut tissue in a larger path around the atherectomy device. Theatherectomy apparatus (2606) may be distally advanced while sweeping, orthe sweeping and distal advancement may be performed as separate steps.

It may be desirable, in conjunction with using the atherectomy apparatusas described above, to introduce into the region a bioactive material,comprising, for example, a restenosis-inhibiting agent, athrombus-inhibiting agent, an anti-inflammatory agent, combinationsthereof and the like. The bioactive material can be introduced as acoating on a balloon that may be expanded into contact with the regionto deliver the bioactive material, and/or may be delivered using theatherectomy apparatus.

The region of restenosis can comprise a peripheral blood vessel, e.g., aperipheral blood vessel in a leg above, at, or below the knee.Additionally, while described immediately above to treat in-stentrestenosis, it should also be appreciated that the methods describedhere may be used to treat restenosis of a vessel that does not include astent.

The foregoing is considered as illustrative only of the principles ofthe invention. Furthermore, since numerous modifications and changeswill readily occur to those skilled in the art, it is not desired tolimit the invention to the exact construction and operation shown anddescribed. While the preferred embodiment has been described, thedetails may be changed without departing from the invention.

We claim:
 1. A method for performing an atherectomy comprising:introducing an atherectomy device into a blood vessel, wherein theatherectomy device comprises a handle, a catheter, and a cutterassembly, wherein the cutter assembly comprises a cutter housing and acutter configured to rotate within the housing, wherein the cuttercomprises at least one helical flute forming a cutting blade having apositive rake angle, wherein the positive rake angle is between 60degrees and 80 degrees, and wherein the cutter comprises a first cuttingelement and a second cutting element, wherein the first cutting elementhas at least a first portion having an outside diameter greater than orequal to an outside diameter of the cutter housing; advancing the cutterassembly to a targeted region having occlusive material; and rotatingthe cutter to cut the occlusive material.
 2. The method of claim 1wherein the positive rake angle is about 70 degrees.
 3. The method ofclaim 1 wherein the first cutting element comprises at least two helicalflutes.
 4. The method of claim 3 wherein the second cutting elementcomprises at least two helical flutes.
 5. The method of claim 1 whereinat least a portion of the first cutter element extends from an openingin the cutter housing.
 6. The method of claim 5 wherein the portion ofthe first cutter element extending from the opening in the cutterhousing has a hemispherical profile.
 7. The method of claim 1 whereinthe cutting blade has a relief angle less than or equal to about 10degrees.
 8. The method of claim 7 wherein the relief angle is about 0degrees.
 9. The method of claim 1 wherein the cutting blade has a fluteangle less than or equal to about 30 degrees.
 10. The method of claim 1wherein the cutting blade has a helix angle between 30 degrees and 60degrees.